CA1194174A - System for tele-locating regenerative repeaters - Google Patents
System for tele-locating regenerative repeatersInfo
- Publication number
- CA1194174A CA1194174A CA000385344A CA385344A CA1194174A CA 1194174 A CA1194174 A CA 1194174A CA 000385344 A CA000385344 A CA 000385344A CA 385344 A CA385344 A CA 385344A CA 1194174 A CA1194174 A CA 1194174A
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- CA
- Canada
- Prior art keywords
- sequence
- tele
- signals
- carrier
- circuit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/40—Monitoring; Testing of relay systems
- H04B17/407—Monitoring; Testing of relay systems without selective localization
- H04B17/408—Monitoring; Testing of relay systems without selective localization using successive loop-backs
Abstract
ABSTRACT:
A transmission path between two terminal stations for transmitting digital information signals at a predeter-mined rate in one direction via a forward path and in the other direction via a return path comprises regenerative transmitting tele-location commands to the repeaters via the forward path, cattier signals of the rate being on-off modulated in this transmitter by means of an amplitude modulator in accordance with output signals of a command sequence generator, and further comprises in every repeater a loop circuit between forward and return paths having an associated control circuit which cooperates with a detector for the presence of carrier signals in the return path for receiving tele-location commands. Without the use of addresses assigned to the repeaters a reliably operating control circuit of a simple structure is obtained in a tele-location system of this type by so arranging the command sequence generator that it produces command sequences which are each formed by a pulse train having at least one pulse, the pulses being transmitted by interrupting the carrier signals by means of the amplitude modulator.
A transmission path between two terminal stations for transmitting digital information signals at a predeter-mined rate in one direction via a forward path and in the other direction via a return path comprises regenerative transmitting tele-location commands to the repeaters via the forward path, cattier signals of the rate being on-off modulated in this transmitter by means of an amplitude modulator in accordance with output signals of a command sequence generator, and further comprises in every repeater a loop circuit between forward and return paths having an associated control circuit which cooperates with a detector for the presence of carrier signals in the return path for receiving tele-location commands. Without the use of addresses assigned to the repeaters a reliably operating control circuit of a simple structure is obtained in a tele-location system of this type by so arranging the command sequence generator that it produces command sequences which are each formed by a pulse train having at least one pulse, the pulses being transmitted by interrupting the carrier signals by means of the amplitude modulator.
Description
~194~'7~
PHFo(~0~51~l 1 16~7.~1 "System for tele-locatinrr regenerative repeaters".
The invention relates to a system for tele-locating regenerative repeaters ~hich are inclu-le(l in a transmission path ~etween two terrninal stations for trarls-mitting at a predetermined rate digital information signals 5 in one ciirection v-ia a ~or~.~ar{1 pa-th and in the other direet~
ion via a return path, one of the terminal sta-tions com-prising a tele-location transmitter for -transmitting tele-location commands to -the repea-ters ~ia the forward path, the transmitter comprising a generator for generating carrier 10 signals at the predetermined rate ancl an amplitude modulator for on-off modulation of saifd carrier signals in accordanee with output signals of a eommand sequence generator, and eaeh repeater eomprising, arranged between forward path and return path~ a loop eircuit with an associated control cir-15 cuit cooperating ,~ith a (le-tector for detecting the presence of carrier signals in the f`orward path for receiving said tele-location commands.
The prior art systems for the remote locatin~ of the repeaters may be cdistinguished in two types, a first type in which a unique address is assigned -to eaeh repeater, and a seeond type in whieh sucll an address is not used~
A systern of the first type is clescribed in German Patent Speeification 22 15 836. In this known system the address eonsists of a uni~ue frequency assignecl to eaeil repeaterO This frequeney is obtained in the tele-location transrmitter by a sui-table choice of the signals for the on-off modulation of the carrier signa1s Recognition of the said frequency in a repeater then accornplishes looping of` the forward and return pa-thsu A firs-t disadvan~age of this type of systern is due to the use of filters for the fre{luency detec-tion~ as f`ilters are llsually t~ulky circu:its llaving ..t dfliclte turlirlgO A Sfcorl(i iisa(lv.~nt(-ge llso results 11941'7~
PHF. 80-514 2 from the use of filters and resides in the fact that said filters must be tuned in a manner which is different for every repeater, which seriously hampers the installation of the repeaters.
A system of the second type is disclosed in German "Auslegeschrift" 26 53 201 by Siemens AG and which was laid open to public inspection on May 24, 1978. In essence, said prior art system employs two kinds of signals:
the signals of the first type are preparatory signals which are transmitted to make the regenerators included in the repeaters suitable for receiving the signals of the second type, which form loop commands. A first disadvantage of this system resides in the fact that two kinds of signals must be generated and recognized in each individual repeater.
A second disadvantage is that each repeater must be pro-vided with a separate transmitter for retransmitting the preparatory signals to the following repeater.
It is an cbject of the invention to provide a tele-locating system defined in the preamble which belongs to the said second type but does not have the disadvantages mentioned in the foregoing.
According to the in~ention, the system for the tele-location of repeaters is characterized in that the command sequence generator is arranged for applying to the control circuits of the repeaters command sequences which are each formed by a pulse train having at least one pulse, which pulses are transmitted by interrupting the carrier signals by means of the amplitude modulator.
The invention is based on the recognition of the fact that the interruptions of the carrier signals are con-verted into pulses by the carrier detector and that it is thus possible to control looping and unlooping of the repeaters by pulse trains with the aid of control circuits having a simple structure which need only process pulses.
The invention and its advantages will now be further described by way of example with reference to embodiments shown in the accompanying drawings, in which:
Fig. 1 shows a simplified block diagram of a tele-locating system in accordance with the invention;
11"3~'7'~
Pl-TF.~0-~14 ~ 1~ 7.~1 Fig. 2 S~lOWS the ~orm ot` the transmitted signal for a b-inary sequence which is convertecl in accordance wi-th the GO de HDB3;
~ ig. 3 shows the L`orm of` a carrier s1gnal em-ployed in -the system of tlle inverltion;
Fig. ~I ShOl`JS an e~ample of the rnanner in ~hich the command sequences are -trarlsrnit-tfcl;
Fifr. . shows the form of the signal at the ou-tput of -the earrier detec-tor when Command sequences of Fig.
lO are employed;
Fig, 6~ Fig. 7, Fig. ~ and Fig. 9 illustrate -the behaviour of the signals in the con-trol circuit of a re-peater in different circumstances;
~ ig. 10 shows a number of signals to explain tlle lS operation of the system of -the invencion;
Fig. 11 shows an example of the command sequences employed in practice;
~ig. 12 shows an embodiment of the command se-quence genera-tor;
Fig. 13 shows a preferred embocliment of the control eireuit in a repeater.
In Fig. 1, a line terminal station 1 is connected to a transmission patll 2 in t~le f`orm of a cable, wherein n repeaters R1, R2, R3, ... Rn are ineluded. This cable haj 25 -two pairs of conductors 3 and 4, the pair 3 forming the path in the forward direction and the pair ~ the path in the return direetion, both considered from line terminal station 1. The repeaters R1, R2, R3, ... Rn have iclentieal structures and only repeater R1 is shown in greater de-tail 3~ in Fig. 1. Repea-ter R1 comprises two input transformers T1 and T2, and two output transformers T3 and T4, f`or -the respective connections to the forwclrd and return paths.
The transf`ormers T1 and T3 are interconnected by a regener-ating circ-uit 10 and the transforrrlers T2 and T~ are inter-35 connected by a regenerating circuit 20. The structllre oftllese regenerating circuits ancl the several signal pro-cessing operatiorls performed -thereill are well kno~m to a person skill-(l in the art anc-~ nee(l no fur-~iler o~plallatiorl.
1~941';~4 PHF.80-514 4 16.7.81 The regenerating circ-uits used in ~-ig. l are formed by an integrated circui-t described in the article "E4uipemen-t de ligne numérique à 2 Mbit/s de cleu~ième génération"
published in "Cables ~ Transmission", ~o. 2, ~pril 1978.
5 In ~lg. 1, two amplifiers for regenerating circuit -lO are shown separately, these amplifiers 21, 22 havirlg for tlleir object -to amplify tlle signais of each polarily for the for-ward path 3 and have an inhibiting input which is connected with a conductor 25. In addition, repeater R1 comprises a 10 loop circuit 30 which, for the sake of simplicity, is shown in Fig. 1 as a relay having -two contacts K1, K2 and two positions P1, P2, which relay is energized bv a signal which is passed to i-ts energizing coll 32 via a conductor 31. When the contacts K1, I~2 are in the position P1, looping of re-15 peater R1 occurs, that is to say -the outputs of amplifiers 21, 22 are connected to the input of regenera-ting circuit 20, and when the contacts K1, K2 are in the position P2, the input of regenerating circuit 20 is connected to the return path 4 via transforrner T2. To energize the relay in 20 loop circuit 30 of repeater R1 -tele-loca-ting commands are transmitted via the forward path 3, which commands are supplied by a tele-locating transmitter 40 in line terminal station 1.
In the above-described e~ample binary information 25 is transmitted at a rate of 2.048 Mbi-t/s by means of the line code HDB3.
~ ig. 2 shows a sequence of binary elerments "1", ~0'~, "1", "0", "0", "0"~ "0", "1", "1", "0",.. . which are transmitted in accordance with this code. This transmitted 30 signal may assume three possible values +V, 0, -V; in addition each binary elemen-t has a iuration T of 433 ns.
The tele-loca-tion transmitter 40 comprises a carrier signal generator 45 whose rate corresponds to the normal transmission rate of 2.048 Mbit/s, and an amplitude 35 modulator 46 for on-off modulation of the said carrier signals in accordance wi-th the output signals of a comnland sequence g~enerator 47. In addition, for the control of loop PllF.80-514 119~74 ~ ., . 81 circuit 30, repeater R1, and likewise all the ~,ther re-peaters, inc'u(le a control circuit ~0, which c~,operates with a detector 51 forMing part of regnerating circui-t lO, this detector 51 detecting the presence of a carrier on the forward path.
In the event of transmission by nlearls of the line code HDB3, -the carrier signal is obtained in a simple way by continuously transmitting the binary elemen~ "1", which results in a sigal that is rich in transitions which can be easily cliscerned in the repeaters: the shape of the signal at the output of ~enerator 45 is shown in Fig. 3, The duration of each ~inary element "1" is of collrse also eqllal to 488 ns.
The tele-locating transmit~er 40 is used in 15 practice only when an unsatisfactory transmission on line path 2 has been detected. The output signals of transmitter 40 are then applied to thelinepath 2 by means of a switch 5~, which is adjusted to such a position that forward path 3 of line path 2 can receive the signals from transmitter 40.
After a start up sequence S0 command sequence generator 47 produces -three sequences S1, S2 and S3.
The firs-t sequence S1 is a valida-tion-sequence to make the control circuits 50 suitable for receiving ~he ne~t se-quences S2 and S3. The second sequence S2 is a looping-25 sequence, that is to say tha-t a loop is formed in all repeaters receiving said sequence S2; it should be noted that at that momen-t repeater R1 may be tested. ~he third sequence S3 is an unlooping-sequence, that is to say that in a selective manner, one after the other, the repeaters 30 R1, R2, R3, ..., Rn can be unlooped in order to test the repeaters R2, R3, ..., respectively. The desired number of repeaters to be unlooped is adjusted by means of a keyboard switch 60 of generator 47.
~ ig. 4 illustrates the manner in which said sequences appear. During the sequence S0, a series of binarv elements "1" is transnli-tted through forward pa~h 3 during some tens of milliseconds to stabilize tlle operatlon of the 11941~74 PH~ . 80- 51 ~ , 81 valicl repea-ters. This series of binar~~ elemen-r s " 1 " forms the carrier signal at`ter lla-ving been convertecl into the line cocle HDB3. During the ~ralidl-tion-senluence SI the ~rarlsnlissior of the carrier signal is in~terrupted f~ll tilnes, each in-ter-5 ruption having a duration of O. 5 rns; -~hese carrier in-ter-ruptions are performed a-t e(luidistant instarlts spaced at a time interval of L; ms.
This sequence S1 is clifficul-t to imi-ta~e, that is to say i-t clearly dif fers frolr! the normall-v transnlit-ted lO digital information signals. Thus, 1oo? circuit 3O is pre-ventecl from establishing an untimely connection between forward path 3 and return path 4. For a~reater certainty, means (which will be described llereinafter) are provided in control circuit 5O so -that in the event rhat inspite of 15 everything imitation would occur, the loop then established will automatically disappear after a prede terrnined period o f t ime .
During the looping-sequence S-' the carrier signal is interrupted for a long period of time which may be longer 20 than or equal to 4 ms.
The unlooping-sequence S3 consists of ashort carrier interruptions of O . 5 ms ~ the number of which depends on the number of repeaters to be unlooped. in response -to the command sequence signals -transmitted over the for- ard path, 25 detector 51 will produce a logic signal A which is shown in ~ig. 5 relati-ve to l?ig. 4. In -the presence of the carrier, logic signal A assumes the value " 1 " and in -the absence of the carrier the value "O" .
This signal A is ap-plied to control circuit 5O.
30 This circui-t 5O comprises a valida-tion circui-t 7O, which after receipt of the validation-sequence produces a logic signal " 1 " during a prede terminecl tirne of sorne seconds.
As a result thereof~ a gate circuit 71 is set to its con-ductive sta-te ~ so that signal A can be passed via a first 35 output of ga-te circuit 71 to an integratillg network in ti~e forrn of a resistor 7~ having va:lue R and a capaci tor 7 3 havirlr, value C ~ ancl a aignal A whi c}- appe.ars lt a second PHF.80-51~l 7 1~).7.81 output of` gate cirouit 71, may be transmitted -to the R-input of a flip-flop 75 of` -the RS-type; as is known such l flip~
flop rnay he in the ~orm of two NA~D-gates. The S-input of this ~li -f`lop 75 is connected tothe integrating ne-~;ork, that is to say -to ti1e comrnon Jnnction of resis-tor 72 ancl capacitor 73.
The other end of resis-tor 72 is connected to the first output of gate circuit 71, while the other enc' of capacito~~ 73 is connec-ted to a vol-tage reference ~oint ~0 (ground). In the non-valid condition~ circui-t 70 produces a logic signal "0"; then a logic "1" occ-urs at the first output of gate circuit 71 and a logic "0" at the second output. The state of flip-flop 75 is then perfectl~r defined.
The Q-output of the flip-flop 75 is connected 15 to conductor 31 and also to aclifferen-tiating network in the form of a capacitor 76 having value C~ ancl a resis-tor 77 having value R~o The output of this differentiating network is connected to one input of an AND~gate 78 having ~;o inputs, the other input being connected to the outpu~ of 20 carri~r detector 51.
The ou-tpu-t of -the differentiating networ'~ is formed by the common junction of capacitor 76 and resistor 77. The other end of capacitor 76 is connected to t.'1e Q-output of flip-flop 75 and the other end of resistor 77 is 25 connected to a fixed voltage source which represents a signal having logic value "1". The outpu-t of ~ND-ga~e 78 is connected to conductor 25.
The operation of control circuit 50 in different circumstances will now be further e~pl.ined with reference 30 to the signal A a-nd the signals ~, D, F and G which occur at the output of integrating network 72, 73, at the Q-ol1tput of flip-flop 75~ at -the 011tpUt of integrating networ~ 76, 77 and on conductor 2 5.
In the following description i-t is ass~lmec1 that 35 validation circuit 70 has already been e~cite-1 and oroduces a logic signal "1".
Witlh reference to ~i~.6 it will l)e describe(-l l1ow ontrol circllit 50 resl)or1<ls -to t~lC interl~up-tion of ~he 1194~'74 PHF~0~514 ~ 16 7.3-l carrier during the sequence S2O It is assumed that t1 is the instant a-t which this carrier in-terruption occurs. Prior to instant t1, signal A and signal B have tlle value "1", signal D has the value "O" whicl1 is imposed by the last interruption of sequence S1, signal F has the -value "1"
and signal C has also the value "1". ~hen signal G has the value t1 ~ the amplifiers 21 and 22 are not blocked. After instant t1, signal A assurnes the value "O" ancl as a result gate circuit 78 is immediately set to its non-conductive lO state so that also signal G assumes ~he value "O", signal B
then starts decreasing at a rate which depends on the value of the time constan-t RC, until at an instant t2 signal Bhas reached a value which corresponds to a logic value "O", taking account of -the value of the threshold Se of the lS circuits employed. Flip-flop 75 then changes state ancl signal D at its Q-output assumes the value "1". The tran-sition from the value "O" -to the value "1" in signal D
causes a sudden increase of signal F, whicl1 in r~sponse thereto presents a voltage peak, but does not loose its 20 logic value "1". A-t instan-t t3, signal A again assumes the value '!1" so that signal ~ also assumes the value "1" again.
Thus, control circuit 5O accomplishes -that the long carrier interruption occurring after the validation-sequence S2 is passed on unmodified to the next repeater.
25 It should be noted that when signal D llas a value "1", this means that the repeater is in the loop condition and con-sequently that the forward path is connected to the return path.
Now, with reference to Fig. 7, there follows 30 a description of a long carrier interruption, which is eomparable to the preceding interruption during the sequence S2, but the repeater being in the loop condition. ~his earrier interruption occurs at an instant tll. Prior to this instant t4, all val-ues of the consiclered signals .lre equal 35 to those prior to theinstant t1 (see Fig. ~ ut with tlle exception o~ course of signal D which has -tlle value "1"
just prior to instan~ t4. From instarlt t4 onwar~ls signal D
il94174 PHF.XO-514 9 16.7.~1 assumes the va:Lue "O", whiciL also holds for the signals G
and F, and the value of signal B decreases until, at an instant t5, -the val1le of the -threshold Se is reached so that signal B is tllereafter assumed t~ have the value "O", 5 causing flip-flop 75 to change state, tha-t is -to say that signal D assumes the value "1" after instant t5. It shoulc1, however, he noted that the rate at ~hich the value of signal B decreases exceeds the ra-te at which the value of signal F
increases. When at instant t5 signal D changes from ~he 10 value "O" t~ the va]ue "1", signal F immediately assumes this value "1", AND-gate 78 then being in the conductive state. So wherl signal A assumes the value "1" at an instant t6, also signal G assumes this value "1" as a result thereof.
Summarizing the above, when a repeater is in the 15 loop condi-tion and ~hen this repaater receives a command pulse (carrier interruption) of a long duration, this command pulse is for~arded as such and this repeater remains in the loop condition.
Now, with reference to Fig. 8, the behaviour of 20 the system ~ill be described for the even-t that a carrier interruption of short duration is receivecl by a repeater in the loop condition.
These carr:ier interruptions occur during the un-looping - sequence S3. This carrier interruption manifests 25 itself in that signal A assumes -the value "O" at an instant t7. Prior to this instant t7, the signals B 7 F and G have the value "1", as has also signal D, for the repeater is then in the loop condition. When at this instant t7 signal A
assumes the value "O", this causes flipflop 75 to change 30 state, so that signal D then assumes the value "O" and the repeater is unlooped. This change in value is then imme-diately passed on by the differentiating network 76, 77, so that signal F then immediately assumes the value "O", and starts to increase -thereafter. In its turn, signal B starts 35 decreasing, but at an instant t8 signal ~ assumes the value "1" again, causing signal B -to return to the vallle "1"
withou~ llaving reaclled tlle -t~lreshold val11e Se. So flip-flop 11~41'7~
P~-IF.80-514 lO l6.7.81 75 does not change state and signal D keeps the value "0".
Signal F starts to increase and at a precletermined instant t9 signal F reaciles a threshold value Se7 aG which ir; is assumed -that signal F has the value "1"; AND-gate 78 i9 tllen rendered corlductive and the value "1" of signal A is pas.sed on, so that signal G assumes -the value "1" C-at instan~ t~.
The repeater whiclh is in the loop condition and receives a short unlooping pulse (carrier interruption~ is unlooped and in its turn transmits a long blocking pulse lO (carrier interruption).
The behaviour of the system for the event that a carrier interruption of a short duration is received by a repeater which has just been brought in the unlooped condi-t-ion will now be explained with reference to Fig. 9. ~his 15 carrier interruption occurs at an instant t10. Prior to this instant, the signals A, B, F and G have the value "1" and signal D has the value "0", so -that when signal A assumes the value "0 at instant t10, this does not have any in-fluence on flip-flop 75 and signal D keeps the value "0".
20 Since signal F has the value "1", signal G follows the value of signal A, This interruption is short relative to the time constant RC, so that signal B does not have sufficient time to reach the threshold value Se at instant t11 at which signal A again assumes the value "1". Since A~D-gate 25 78 remains conductive, signal G reproduces the changes in the value of signal A.
A repeater which is in the unlooped condition and receives a short carrler interruption remains in the unlooped condition and passes this brief command pulse 30 unmodified to the next repeater.
It is now possible to describe the operation of the tele-locating system of the invention in a simple way with reference to Fig. 10. In Fig. 10, ST is tlle signal at the output of line terrninal station 1, SR1 is the signal 35 at the output of repeater R1 and SR2 -the signal at ~he out-put of repeater R2. Si~nal VAL in Fig. lO is -the valida-tion signal which will not be shown ~or e-very repeater.
~9~7~
PHF.~0~ .7.,~1 In addi tion7 ~ig. 1 0 S}lOWS -t1le signaLs D1, D2 anfl D. W]liC~I
control looping .^ln~.l unlooping ~ithin the repeaters R1, R2 and R3, respectively.
Signal ST is shown al:ready in Figure 3, as are also tlle differellt comman-l sequences S0, S1, S2 and S3 Validation signal VAL cl1anges to ~he value "1"
during the sequence S1 l~hic:h star-ts at ins-tan-t t20 (at which the secluence S0 stops? anri stops at Lnstan-t T21 (at ~,hich the sequence S2 starts). The sequences S0 and S1 are :touncl 10 back unmodified in the signals SR1 and SR2. I~hen a~ instant t21 in the sequence S2 the long interrupti.on of the carrier signal sta.rts~ this carrier irlterruption causes looping of the repeaters which can receive the sequence S2. This loop-ing operation is no-t of necessitv perf`ormed sim1.ll-taneouslv, 15 which otherwise cloes not negatively aifect the o-peration of t:he system. It may, however, be assumed that at an instant t23 t}-lese repeaters are in the .Looped condition and tha-t -then the signals Dl, D2 and D3 assume the value "1".
From that instant onwards repeater R1 may be tested~ as 20 mentioned in the foregoing.
The sequence S3 starts at instant t24. A first short carrier interruption IP1 appears at instant t2~.
In the region of repeater R1 this interrup-tion IP1 nas a double effect: on the one hand IP-1 cause unlooping of this 25 repeater and on -the other hancl IP1 ca1lses the carrie-r in this repeater -to be blocked in such a Wcly that -the hrief in.terruption IP1 is converted into an interruption of a long duration IPL1. The long carrier interruption IPL1 ~iill effec-t looping of the repea-ter R2 a-t the installt t26; signal D2 30 which assumed the value "0" at instant t25 then assumes the value "1" a~ain. This interruption IPL1 ~ill be transmittecl to all the repeaters so that the-v will be in the loope~l condition. After ins-tarlt t2~ it is possible to tes~ repeater R2.
At an in.stant t2, a secollcl short carricr inter-rup-tion IP2 o:t` the sequerlce S3 appears at tlle 011tpUt ot~
line statior1 1. T]-lis ~nterr1lptiorl IP2 i.s trans111itte(1 ;is SUC~l PHF.8O-514 ~ 1914 } Y~ 16.7.81 by repeater R1 and wil1 l)e collvertecl into a long inter-ruption IPI,2 by repeater R2. This long interruption IPL2 will thus be -transmitted to all the follo-wing repeaters.
So the interruption IP2 causes unlooping of re~eater R2 so that it is then possible to test repea-ter R3. The third short carrier inter~lption IP3 appearing at an instaIlt -t2~
wiil then unloop repeater X3 in the manner described in the foregoing, so that the test of-the repeater after R3 can be performed~ this interruption IP3 being transmitted as such 10 by the repea-ters R1 and ~2.
The number of short carrier interruptions trans-mitted by tele-locating transmitter 4O during -the sequence S3 thus determines the number of repeaters to be unlooped.
A sequence So may be substituted for start up 15 sequence SO. This sequence SO is shown in Fig. 11, in combination wi-tll the sequences S1, S2 and S3, and includes short carrier interruptions IP1 , IP2 , IP3 of the same nature and in the same number as the carrier interruptions IP1, IP2 and IP3. As mentioned in the foregoing, this 20 number is equal to the number of repea-ters one wants to unloop. The importance of such a sequence SO resides in the fact th~t this sequence ensures that all the repeaters located upstreams (that is to say in the direction towards line terminal station 1) of the repeater to be testecl have 25 indeed been unlooped and have so irrespective of the logic state of the control circuits in the upstream repeaters.
Thus, validation-secluence S1 will be properly observed and certainty will be obtained abou-t the durati~n of the vali-dation, as will be explained hereafter.
The embodiment shown in Fig.12 of the command sequence generator 47 in line terminal station 1 comprises a generator 9O generating periodic signals which cletermine the fdifferent elementary instants for the sequences to be formed. The output of generator 9O is connected to the 35 input of a first divider 92 the output of which is connected to the inpu-t of a second divider 94. rhe output of` divider 92 constitutes the output of commancl sellufnce generator 47.
1~41'~'4 PHE`.~30-514 l3 16.7.8l These dividers 92 and 94 are variable clividers, that is to say that the frequency of the signals a t -their outputs is equal to the frequency of the signals at their inputs divided by a number presen-t at their control inputs 95 and 96. Different numbers may be applied to the control inputs 95 and 96. F`or example, the numbers "64", "8", "16", "54"
~ay be applied to input 95 while a number N represen~ing the number of repeaters to be unlooped may be applied to input 96, this number ~T being adjusted by keyboard switch 60, In addition, also the numbers "64" and "2" may be applied to input 96. A counter 97 counts the pulses in the output signal of divider 94 and sequentially controls two switches 9~ and 99 in such a way that the divisions with different dividends are sequentially perfcrrmed.
The sequence So is formed in the following manner. On the one hand, a division by "64" is performed in divic'er 92 and on the other hand a division by "~i" in divider 94. The signal at the output of command sequence generator 47 becomes active as soon as "64" elementarv instants have been counted. This is repeated "N" times, whereafter there appears at the output of divider 94 a pulse which causes the content of counter 97 to be in-creased one step, in response to which the transition to the next sequence takes place.
This ne~ct sequence is the validation-sequence S1 which is formed when the number "8" occurs at input 95 of divider 92 and the number "64" at input 96 of divider 94.
Thus, a carrier interruption having an elementary duration will take place oncé in each group of eight elementary instants. This is repeated 64 times, whereafter the transition to sequence S2 takes place.
The looping--sequence S2 is formecl when the number "15" occurs at input 95 of divider 92 and the number "2" at input 96 of` clivider 94.
The unlooping-sequence S3 is therea~ter f`ormed in a similar manner as sequence SO~.
~194~17~
P~IF.80-514 'I'~ 16.7.81 Fig. 13 is a schematie representation of a practica] embodiment of` control circuit 50 of the repeatersO
In the f'`irst place, Fig. 13 SILOWS in detail validation eireuit 70 wl-lich is formed on the basis of the eircuit known 5 in the technique as a "diode -transis-tor pump". So this cir-cuit 70 eomprises a PNP-transistor 100 ~ith a cIiocle 101~
~hose anode is conneeted to the base of transistor 100 and ~hose cathode is connectecl to the emitter. The emitter of transistor 100 is connected tothe outpu-~ of carrier cle-tector I0 51 in regenera-ting eireuit 'l00 via a capacitor -l02 having capacitanee C1. The eolleetor of transistor 100 eons-titutes the output of eircuit 70 and is connected -to a voltage reference point (ground) via a capaeitor 103 having eapa-eitance C2 whicll is shuntecl by a resislor 104 having value 15 R2. ~ voltage Vce is applied betweeli-the ~ase oftransistor 'lOO
and the voltage reference point (grouncl).
The carrier interruptions produce a voltage of "0" volt at the outpu-t of detector 51, w3lile the presence of the carrier resul-ts in a voltage of Vec volt. Thus, at 20every carrier interruption eapaeitor 10' is ehargecl to a voltage Vec, thereafter in the presence of -the carrier a eharge -transfer from capacitor 102 to capacitor 103 oeeurs, so that the voltage at the terminals of eapaeitor 103 will inerease by a quanti-ty whiel-l is proportional to the ratio 25C1/C2 and -to the voltage Vee. When the voltage aeross eapaeitor 103 reaehes a precletermined threshold -value this voltage is eonsidered as a logie value "1". Resis-tor 104 is ehosen so that the time eonstant R2,C~ is large relative to the period of the interruptions during -tlle validation-30sequenee S1. Tllis resistor 104 makes it possib]e to havethe validation signal deerease to the value zero after a predetermined periocl of time. As a result thereof in~er-ventions are avoide-l if during a normaL transmission of information -the validation-sequenceis irnitated. It is also 35im~ortant tl1at tlle valiclation signal l~as the predetermined duration. To ensure this it is neeessary tha-t the capaeitor 103 is well-ellarged. This implies tha-t all carrier inter-ruptions are properly reoeived ~y -the repea-ter which 1194~'~4 PHF.80-5l4 l5 16.7.S1 comprises this control circui-t 50. The importance of the use of the above-clescribed sequence SO~ will then ~e clear.
In ~'ig. 13, the gate circui-t 7l o~` control circuit 50 is formed by two inver-ters 110 and11l~ a NAND-ga-~e 112 and a NOR-gate 113. The OUtpllt of N~ND-gate 112 is connected to the input of the in-tegrating network in the forM of r--sistor 72 and capacitor 737 wilile the 01ltpUt of NOR-gate 113 is connected -to the R-input of flip-~lop 75, which itself is t`ormed by -two NAND-ga-tes 115 and 116. One input ofthe ga-tes lO 112, 113 is connected to the output of cletector 51 v~a an inverter 110; the other input of NAND-gate 112 is dir~ctly connected to the output of validation circuit 70 and the other inpu-t of NOR-gate l13 is cGnnected to the output o~
validation circuit 70 via an inverter111. In aclditioll, 15 a protection resistor 120 is provided ~etween -the ou~put of the clifferen-tiating networl~ (in the form of capacitor 76 and resistor 77) ancd the input of AND-ga-te ',~8.
In the regenerating circuits of the conven~ional type, there are often provided amplitude cletectors for the 20 signals present on tl~e path -to which the circuit is connec-ted. These regenerating circuits may also comprise a deteetor for producing a signal ~hich indicates the pre-sence of regenerated clock signals. Within the frame work of the invention it is advantageous to use either the 25 amplitude detector or the last-men~ioned presence de~ec-tor as a carrier detec-tor.
PHFo(~0~51~l 1 16~7.~1 "System for tele-locatinrr regenerative repeaters".
The invention relates to a system for tele-locating regenerative repeaters ~hich are inclu-le(l in a transmission path ~etween two terrninal stations for trarls-mitting at a predetermined rate digital information signals 5 in one ciirection v-ia a ~or~.~ar{1 pa-th and in the other direet~
ion via a return path, one of the terminal sta-tions com-prising a tele-location transmitter for -transmitting tele-location commands to -the repea-ters ~ia the forward path, the transmitter comprising a generator for generating carrier 10 signals at the predetermined rate ancl an amplitude modulator for on-off modulation of saifd carrier signals in accordanee with output signals of a eommand sequence generator, and eaeh repeater eomprising, arranged between forward path and return path~ a loop eircuit with an associated control cir-15 cuit cooperating ,~ith a (le-tector for detecting the presence of carrier signals in the f`orward path for receiving said tele-location commands.
The prior art systems for the remote locatin~ of the repeaters may be cdistinguished in two types, a first type in which a unique address is assigned -to eaeh repeater, and a seeond type in whieh sucll an address is not used~
A systern of the first type is clescribed in German Patent Speeification 22 15 836. In this known system the address eonsists of a uni~ue frequency assignecl to eaeil repeaterO This frequeney is obtained in the tele-location transrmitter by a sui-table choice of the signals for the on-off modulation of the carrier signa1s Recognition of the said frequency in a repeater then accornplishes looping of` the forward and return pa-thsu A firs-t disadvan~age of this type of systern is due to the use of filters for the fre{luency detec-tion~ as f`ilters are llsually t~ulky circu:its llaving ..t dfliclte turlirlgO A Sfcorl(i iisa(lv.~nt(-ge llso results 11941'7~
PHF. 80-514 2 from the use of filters and resides in the fact that said filters must be tuned in a manner which is different for every repeater, which seriously hampers the installation of the repeaters.
A system of the second type is disclosed in German "Auslegeschrift" 26 53 201 by Siemens AG and which was laid open to public inspection on May 24, 1978. In essence, said prior art system employs two kinds of signals:
the signals of the first type are preparatory signals which are transmitted to make the regenerators included in the repeaters suitable for receiving the signals of the second type, which form loop commands. A first disadvantage of this system resides in the fact that two kinds of signals must be generated and recognized in each individual repeater.
A second disadvantage is that each repeater must be pro-vided with a separate transmitter for retransmitting the preparatory signals to the following repeater.
It is an cbject of the invention to provide a tele-locating system defined in the preamble which belongs to the said second type but does not have the disadvantages mentioned in the foregoing.
According to the in~ention, the system for the tele-location of repeaters is characterized in that the command sequence generator is arranged for applying to the control circuits of the repeaters command sequences which are each formed by a pulse train having at least one pulse, which pulses are transmitted by interrupting the carrier signals by means of the amplitude modulator.
The invention is based on the recognition of the fact that the interruptions of the carrier signals are con-verted into pulses by the carrier detector and that it is thus possible to control looping and unlooping of the repeaters by pulse trains with the aid of control circuits having a simple structure which need only process pulses.
The invention and its advantages will now be further described by way of example with reference to embodiments shown in the accompanying drawings, in which:
Fig. 1 shows a simplified block diagram of a tele-locating system in accordance with the invention;
11"3~'7'~
Pl-TF.~0-~14 ~ 1~ 7.~1 Fig. 2 S~lOWS the ~orm ot` the transmitted signal for a b-inary sequence which is convertecl in accordance wi-th the GO de HDB3;
~ ig. 3 shows the L`orm of` a carrier s1gnal em-ployed in -the system of tlle inverltion;
Fig. ~I ShOl`JS an e~ample of the rnanner in ~hich the command sequences are -trarlsrnit-tfcl;
Fifr. . shows the form of the signal at the ou-tput of -the earrier detec-tor when Command sequences of Fig.
lO are employed;
Fig, 6~ Fig. 7, Fig. ~ and Fig. 9 illustrate -the behaviour of the signals in the con-trol circuit of a re-peater in different circumstances;
~ ig. 10 shows a number of signals to explain tlle lS operation of the system of -the invencion;
Fig. 11 shows an example of the command sequences employed in practice;
~ig. 12 shows an embodiment of the command se-quence genera-tor;
Fig. 13 shows a preferred embocliment of the control eireuit in a repeater.
In Fig. 1, a line terminal station 1 is connected to a transmission patll 2 in t~le f`orm of a cable, wherein n repeaters R1, R2, R3, ... Rn are ineluded. This cable haj 25 -two pairs of conductors 3 and 4, the pair 3 forming the path in the forward direction and the pair ~ the path in the return direetion, both considered from line terminal station 1. The repeaters R1, R2, R3, ... Rn have iclentieal structures and only repeater R1 is shown in greater de-tail 3~ in Fig. 1. Repea-ter R1 comprises two input transformers T1 and T2, and two output transformers T3 and T4, f`or -the respective connections to the forwclrd and return paths.
The transf`ormers T1 and T3 are interconnected by a regener-ating circ-uit 10 and the transforrrlers T2 and T~ are inter-35 connected by a regenerating circuit 20. The structllre oftllese regenerating circuits ancl the several signal pro-cessing operatiorls performed -thereill are well kno~m to a person skill-(l in the art anc-~ nee(l no fur-~iler o~plallatiorl.
1~941';~4 PHF.80-514 4 16.7.81 The regenerating circ-uits used in ~-ig. l are formed by an integrated circui-t described in the article "E4uipemen-t de ligne numérique à 2 Mbit/s de cleu~ième génération"
published in "Cables ~ Transmission", ~o. 2, ~pril 1978.
5 In ~lg. 1, two amplifiers for regenerating circuit -lO are shown separately, these amplifiers 21, 22 havirlg for tlleir object -to amplify tlle signais of each polarily for the for-ward path 3 and have an inhibiting input which is connected with a conductor 25. In addition, repeater R1 comprises a 10 loop circuit 30 which, for the sake of simplicity, is shown in Fig. 1 as a relay having -two contacts K1, K2 and two positions P1, P2, which relay is energized bv a signal which is passed to i-ts energizing coll 32 via a conductor 31. When the contacts K1, I~2 are in the position P1, looping of re-15 peater R1 occurs, that is to say -the outputs of amplifiers 21, 22 are connected to the input of regenera-ting circuit 20, and when the contacts K1, K2 are in the position P2, the input of regenerating circuit 20 is connected to the return path 4 via transforrner T2. To energize the relay in 20 loop circuit 30 of repeater R1 -tele-loca-ting commands are transmitted via the forward path 3, which commands are supplied by a tele-locating transmitter 40 in line terminal station 1.
In the above-described e~ample binary information 25 is transmitted at a rate of 2.048 Mbi-t/s by means of the line code HDB3.
~ ig. 2 shows a sequence of binary elerments "1", ~0'~, "1", "0", "0", "0"~ "0", "1", "1", "0",.. . which are transmitted in accordance with this code. This transmitted 30 signal may assume three possible values +V, 0, -V; in addition each binary elemen-t has a iuration T of 433 ns.
The tele-loca-tion transmitter 40 comprises a carrier signal generator 45 whose rate corresponds to the normal transmission rate of 2.048 Mbit/s, and an amplitude 35 modulator 46 for on-off modulation of the said carrier signals in accordance wi-th the output signals of a comnland sequence g~enerator 47. In addition, for the control of loop PllF.80-514 119~74 ~ ., . 81 circuit 30, repeater R1, and likewise all the ~,ther re-peaters, inc'u(le a control circuit ~0, which c~,operates with a detector 51 forMing part of regnerating circui-t lO, this detector 51 detecting the presence of a carrier on the forward path.
In the event of transmission by nlearls of the line code HDB3, -the carrier signal is obtained in a simple way by continuously transmitting the binary elemen~ "1", which results in a sigal that is rich in transitions which can be easily cliscerned in the repeaters: the shape of the signal at the output of ~enerator 45 is shown in Fig. 3, The duration of each ~inary element "1" is of collrse also eqllal to 488 ns.
The tele-locating transmit~er 40 is used in 15 practice only when an unsatisfactory transmission on line path 2 has been detected. The output signals of transmitter 40 are then applied to thelinepath 2 by means of a switch 5~, which is adjusted to such a position that forward path 3 of line path 2 can receive the signals from transmitter 40.
After a start up sequence S0 command sequence generator 47 produces -three sequences S1, S2 and S3.
The firs-t sequence S1 is a valida-tion-sequence to make the control circuits 50 suitable for receiving ~he ne~t se-quences S2 and S3. The second sequence S2 is a looping-25 sequence, that is to say tha-t a loop is formed in all repeaters receiving said sequence S2; it should be noted that at that momen-t repeater R1 may be tested. ~he third sequence S3 is an unlooping-sequence, that is to say that in a selective manner, one after the other, the repeaters 30 R1, R2, R3, ..., Rn can be unlooped in order to test the repeaters R2, R3, ..., respectively. The desired number of repeaters to be unlooped is adjusted by means of a keyboard switch 60 of generator 47.
~ ig. 4 illustrates the manner in which said sequences appear. During the sequence S0, a series of binarv elements "1" is transnli-tted through forward pa~h 3 during some tens of milliseconds to stabilize tlle operatlon of the 11941~74 PH~ . 80- 51 ~ , 81 valicl repea-ters. This series of binar~~ elemen-r s " 1 " forms the carrier signal at`ter lla-ving been convertecl into the line cocle HDB3. During the ~ralidl-tion-senluence SI the ~rarlsnlissior of the carrier signal is in~terrupted f~ll tilnes, each in-ter-5 ruption having a duration of O. 5 rns; -~hese carrier in-ter-ruptions are performed a-t e(luidistant instarlts spaced at a time interval of L; ms.
This sequence S1 is clifficul-t to imi-ta~e, that is to say i-t clearly dif fers frolr! the normall-v transnlit-ted lO digital information signals. Thus, 1oo? circuit 3O is pre-ventecl from establishing an untimely connection between forward path 3 and return path 4. For a~reater certainty, means (which will be described llereinafter) are provided in control circuit 5O so -that in the event rhat inspite of 15 everything imitation would occur, the loop then established will automatically disappear after a prede terrnined period o f t ime .
During the looping-sequence S-' the carrier signal is interrupted for a long period of time which may be longer 20 than or equal to 4 ms.
The unlooping-sequence S3 consists of ashort carrier interruptions of O . 5 ms ~ the number of which depends on the number of repeaters to be unlooped. in response -to the command sequence signals -transmitted over the for- ard path, 25 detector 51 will produce a logic signal A which is shown in ~ig. 5 relati-ve to l?ig. 4. In -the presence of the carrier, logic signal A assumes the value " 1 " and in -the absence of the carrier the value "O" .
This signal A is ap-plied to control circuit 5O.
30 This circui-t 5O comprises a valida-tion circui-t 7O, which after receipt of the validation-sequence produces a logic signal " 1 " during a prede terminecl tirne of sorne seconds.
As a result thereof~ a gate circuit 71 is set to its con-ductive sta-te ~ so that signal A can be passed via a first 35 output of ga-te circuit 71 to an integratillg network in ti~e forrn of a resistor 7~ having va:lue R and a capaci tor 7 3 havirlr, value C ~ ancl a aignal A whi c}- appe.ars lt a second PHF.80-51~l 7 1~).7.81 output of` gate cirouit 71, may be transmitted -to the R-input of a flip-flop 75 of` -the RS-type; as is known such l flip~
flop rnay he in the ~orm of two NA~D-gates. The S-input of this ~li -f`lop 75 is connected tothe integrating ne-~;ork, that is to say -to ti1e comrnon Jnnction of resis-tor 72 ancl capacitor 73.
The other end of resis-tor 72 is connected to the first output of gate circuit 71, while the other enc' of capacito~~ 73 is connec-ted to a vol-tage reference ~oint ~0 (ground). In the non-valid condition~ circui-t 70 produces a logic signal "0"; then a logic "1" occ-urs at the first output of gate circuit 71 and a logic "0" at the second output. The state of flip-flop 75 is then perfectl~r defined.
The Q-output of the flip-flop 75 is connected 15 to conductor 31 and also to aclifferen-tiating network in the form of a capacitor 76 having value C~ ancl a resis-tor 77 having value R~o The output of this differentiating network is connected to one input of an AND~gate 78 having ~;o inputs, the other input being connected to the outpu~ of 20 carri~r detector 51.
The ou-tpu-t of -the differentiating networ'~ is formed by the common junction of capacitor 76 and resistor 77. The other end of capacitor 76 is connected to t.'1e Q-output of flip-flop 75 and the other end of resistor 77 is 25 connected to a fixed voltage source which represents a signal having logic value "1". The outpu-t of ~ND-ga~e 78 is connected to conductor 25.
The operation of control circuit 50 in different circumstances will now be further e~pl.ined with reference 30 to the signal A a-nd the signals ~, D, F and G which occur at the output of integrating network 72, 73, at the Q-ol1tput of flip-flop 75~ at -the 011tpUt of integrating networ~ 76, 77 and on conductor 2 5.
In the following description i-t is ass~lmec1 that 35 validation circuit 70 has already been e~cite-1 and oroduces a logic signal "1".
Witlh reference to ~i~.6 it will l)e describe(-l l1ow ontrol circllit 50 resl)or1<ls -to t~lC interl~up-tion of ~he 1194~'74 PHF~0~514 ~ 16 7.3-l carrier during the sequence S2O It is assumed that t1 is the instant a-t which this carrier in-terruption occurs. Prior to instant t1, signal A and signal B have tlle value "1", signal D has the value "O" whicl1 is imposed by the last interruption of sequence S1, signal F has the -value "1"
and signal C has also the value "1". ~hen signal G has the value t1 ~ the amplifiers 21 and 22 are not blocked. After instant t1, signal A assurnes the value "O" ancl as a result gate circuit 78 is immediately set to its non-conductive lO state so that also signal G assumes ~he value "O", signal B
then starts decreasing at a rate which depends on the value of the time constan-t RC, until at an instant t2 signal Bhas reached a value which corresponds to a logic value "O", taking account of -the value of the threshold Se of the lS circuits employed. Flip-flop 75 then changes state ancl signal D at its Q-output assumes the value "1". The tran-sition from the value "O" -to the value "1" in signal D
causes a sudden increase of signal F, whicl1 in r~sponse thereto presents a voltage peak, but does not loose its 20 logic value "1". A-t instan-t t3, signal A again assumes the value '!1" so that signal ~ also assumes the value "1" again.
Thus, control circuit 5O accomplishes -that the long carrier interruption occurring after the validation-sequence S2 is passed on unmodified to the next repeater.
25 It should be noted that when signal D llas a value "1", this means that the repeater is in the loop condition and con-sequently that the forward path is connected to the return path.
Now, with reference to Fig. 7, there follows 30 a description of a long carrier interruption, which is eomparable to the preceding interruption during the sequence S2, but the repeater being in the loop condition. ~his earrier interruption occurs at an instant tll. Prior to this instant t4, all val-ues of the consiclered signals .lre equal 35 to those prior to theinstant t1 (see Fig. ~ ut with tlle exception o~ course of signal D which has -tlle value "1"
just prior to instan~ t4. From instarlt t4 onwar~ls signal D
il94174 PHF.XO-514 9 16.7.~1 assumes the va:Lue "O", whiciL also holds for the signals G
and F, and the value of signal B decreases until, at an instant t5, -the val1le of the -threshold Se is reached so that signal B is tllereafter assumed t~ have the value "O", 5 causing flip-flop 75 to change state, tha-t is -to say that signal D assumes the value "1" after instant t5. It shoulc1, however, he noted that the rate at ~hich the value of signal B decreases exceeds the ra-te at which the value of signal F
increases. When at instant t5 signal D changes from ~he 10 value "O" t~ the va]ue "1", signal F immediately assumes this value "1", AND-gate 78 then being in the conductive state. So wherl signal A assumes the value "1" at an instant t6, also signal G assumes this value "1" as a result thereof.
Summarizing the above, when a repeater is in the 15 loop condi-tion and ~hen this repaater receives a command pulse (carrier interruption) of a long duration, this command pulse is for~arded as such and this repeater remains in the loop condition.
Now, with reference to Fig. 8, the behaviour of 20 the system ~ill be described for the even-t that a carrier interruption of short duration is receivecl by a repeater in the loop condition.
These carr:ier interruptions occur during the un-looping - sequence S3. This carrier interruption manifests 25 itself in that signal A assumes -the value "O" at an instant t7. Prior to this instant t7, the signals B 7 F and G have the value "1", as has also signal D, for the repeater is then in the loop condition. When at this instant t7 signal A
assumes the value "O", this causes flipflop 75 to change 30 state, so that signal D then assumes the value "O" and the repeater is unlooped. This change in value is then imme-diately passed on by the differentiating network 76, 77, so that signal F then immediately assumes the value "O", and starts to increase -thereafter. In its turn, signal B starts 35 decreasing, but at an instant t8 signal ~ assumes the value "1" again, causing signal B -to return to the vallle "1"
withou~ llaving reaclled tlle -t~lreshold val11e Se. So flip-flop 11~41'7~
P~-IF.80-514 lO l6.7.81 75 does not change state and signal D keeps the value "0".
Signal F starts to increase and at a precletermined instant t9 signal F reaciles a threshold value Se7 aG which ir; is assumed -that signal F has the value "1"; AND-gate 78 i9 tllen rendered corlductive and the value "1" of signal A is pas.sed on, so that signal G assumes -the value "1" C-at instan~ t~.
The repeater whiclh is in the loop condition and receives a short unlooping pulse (carrier interruption~ is unlooped and in its turn transmits a long blocking pulse lO (carrier interruption).
The behaviour of the system for the event that a carrier interruption of a short duration is received by a repeater which has just been brought in the unlooped condi-t-ion will now be explained with reference to Fig. 9. ~his 15 carrier interruption occurs at an instant t10. Prior to this instant, the signals A, B, F and G have the value "1" and signal D has the value "0", so -that when signal A assumes the value "0 at instant t10, this does not have any in-fluence on flip-flop 75 and signal D keeps the value "0".
20 Since signal F has the value "1", signal G follows the value of signal A, This interruption is short relative to the time constant RC, so that signal B does not have sufficient time to reach the threshold value Se at instant t11 at which signal A again assumes the value "1". Since A~D-gate 25 78 remains conductive, signal G reproduces the changes in the value of signal A.
A repeater which is in the unlooped condition and receives a short carrler interruption remains in the unlooped condition and passes this brief command pulse 30 unmodified to the next repeater.
It is now possible to describe the operation of the tele-locating system of the invention in a simple way with reference to Fig. 10. In Fig. 10, ST is tlle signal at the output of line terrninal station 1, SR1 is the signal 35 at the output of repeater R1 and SR2 -the signal at ~he out-put of repeater R2. Si~nal VAL in Fig. lO is -the valida-tion signal which will not be shown ~or e-very repeater.
~9~7~
PHF.~0~ .7.,~1 In addi tion7 ~ig. 1 0 S}lOWS -t1le signaLs D1, D2 anfl D. W]liC~I
control looping .^ln~.l unlooping ~ithin the repeaters R1, R2 and R3, respectively.
Signal ST is shown al:ready in Figure 3, as are also tlle differellt comman-l sequences S0, S1, S2 and S3 Validation signal VAL cl1anges to ~he value "1"
during the sequence S1 l~hic:h star-ts at ins-tan-t t20 (at which the secluence S0 stops? anri stops at Lnstan-t T21 (at ~,hich the sequence S2 starts). The sequences S0 and S1 are :touncl 10 back unmodified in the signals SR1 and SR2. I~hen a~ instant t21 in the sequence S2 the long interrupti.on of the carrier signal sta.rts~ this carrier irlterruption causes looping of the repeaters which can receive the sequence S2. This loop-ing operation is no-t of necessitv perf`ormed sim1.ll-taneouslv, 15 which otherwise cloes not negatively aifect the o-peration of t:he system. It may, however, be assumed that at an instant t23 t}-lese repeaters are in the .Looped condition and tha-t -then the signals Dl, D2 and D3 assume the value "1".
From that instant onwards repeater R1 may be tested~ as 20 mentioned in the foregoing.
The sequence S3 starts at instant t24. A first short carrier interruption IP1 appears at instant t2~.
In the region of repeater R1 this interrup-tion IP1 nas a double effect: on the one hand IP-1 cause unlooping of this 25 repeater and on -the other hancl IP1 ca1lses the carrie-r in this repeater -to be blocked in such a Wcly that -the hrief in.terruption IP1 is converted into an interruption of a long duration IPL1. The long carrier interruption IPL1 ~iill effec-t looping of the repea-ter R2 a-t the installt t26; signal D2 30 which assumed the value "0" at instant t25 then assumes the value "1" a~ain. This interruption IPL1 ~ill be transmittecl to all the repeaters so that the-v will be in the loope~l condition. After ins-tarlt t2~ it is possible to tes~ repeater R2.
At an in.stant t2, a secollcl short carricr inter-rup-tion IP2 o:t` the sequerlce S3 appears at tlle 011tpUt ot~
line statior1 1. T]-lis ~nterr1lptiorl IP2 i.s trans111itte(1 ;is SUC~l PHF.8O-514 ~ 1914 } Y~ 16.7.81 by repeater R1 and wil1 l)e collvertecl into a long inter-ruption IPI,2 by repeater R2. This long interruption IPL2 will thus be -transmitted to all the follo-wing repeaters.
So the interruption IP2 causes unlooping of re~eater R2 so that it is then possible to test repea-ter R3. The third short carrier inter~lption IP3 appearing at an instaIlt -t2~
wiil then unloop repeater X3 in the manner described in the foregoing, so that the test of-the repeater after R3 can be performed~ this interruption IP3 being transmitted as such 10 by the repea-ters R1 and ~2.
The number of short carrier interruptions trans-mitted by tele-locating transmitter 4O during -the sequence S3 thus determines the number of repeaters to be unlooped.
A sequence So may be substituted for start up 15 sequence SO. This sequence SO is shown in Fig. 11, in combination wi-tll the sequences S1, S2 and S3, and includes short carrier interruptions IP1 , IP2 , IP3 of the same nature and in the same number as the carrier interruptions IP1, IP2 and IP3. As mentioned in the foregoing, this 20 number is equal to the number of repea-ters one wants to unloop. The importance of such a sequence SO resides in the fact th~t this sequence ensures that all the repeaters located upstreams (that is to say in the direction towards line terminal station 1) of the repeater to be testecl have 25 indeed been unlooped and have so irrespective of the logic state of the control circuits in the upstream repeaters.
Thus, validation-secluence S1 will be properly observed and certainty will be obtained abou-t the durati~n of the vali-dation, as will be explained hereafter.
The embodiment shown in Fig.12 of the command sequence generator 47 in line terminal station 1 comprises a generator 9O generating periodic signals which cletermine the fdifferent elementary instants for the sequences to be formed. The output of generator 9O is connected to the 35 input of a first divider 92 the output of which is connected to the inpu-t of a second divider 94. rhe output of` divider 92 constitutes the output of commancl sellufnce generator 47.
1~41'~'4 PHE`.~30-514 l3 16.7.8l These dividers 92 and 94 are variable clividers, that is to say that the frequency of the signals a t -their outputs is equal to the frequency of the signals at their inputs divided by a number presen-t at their control inputs 95 and 96. Different numbers may be applied to the control inputs 95 and 96. F`or example, the numbers "64", "8", "16", "54"
~ay be applied to input 95 while a number N represen~ing the number of repeaters to be unlooped may be applied to input 96, this number ~T being adjusted by keyboard switch 60, In addition, also the numbers "64" and "2" may be applied to input 96. A counter 97 counts the pulses in the output signal of divider 94 and sequentially controls two switches 9~ and 99 in such a way that the divisions with different dividends are sequentially perfcrrmed.
The sequence So is formed in the following manner. On the one hand, a division by "64" is performed in divic'er 92 and on the other hand a division by "~i" in divider 94. The signal at the output of command sequence generator 47 becomes active as soon as "64" elementarv instants have been counted. This is repeated "N" times, whereafter there appears at the output of divider 94 a pulse which causes the content of counter 97 to be in-creased one step, in response to which the transition to the next sequence takes place.
This ne~ct sequence is the validation-sequence S1 which is formed when the number "8" occurs at input 95 of divider 92 and the number "64" at input 96 of divider 94.
Thus, a carrier interruption having an elementary duration will take place oncé in each group of eight elementary instants. This is repeated 64 times, whereafter the transition to sequence S2 takes place.
The looping--sequence S2 is formecl when the number "15" occurs at input 95 of divider 92 and the number "2" at input 96 of` clivider 94.
The unlooping-sequence S3 is therea~ter f`ormed in a similar manner as sequence SO~.
~194~17~
P~IF.80-514 'I'~ 16.7.81 Fig. 13 is a schematie representation of a practica] embodiment of` control circuit 50 of the repeatersO
In the f'`irst place, Fig. 13 SILOWS in detail validation eireuit 70 wl-lich is formed on the basis of the eircuit known 5 in the technique as a "diode -transis-tor pump". So this cir-cuit 70 eomprises a PNP-transistor 100 ~ith a cIiocle 101~
~hose anode is conneeted to the base of transistor 100 and ~hose cathode is connectecl to the emitter. The emitter of transistor 100 is connected tothe outpu-~ of carrier cle-tector I0 51 in regenera-ting eireuit 'l00 via a capacitor -l02 having capacitanee C1. The eolleetor of transistor 100 eons-titutes the output of eircuit 70 and is connected -to a voltage reference point (ground) via a capaeitor 103 having eapa-eitance C2 whicll is shuntecl by a resislor 104 having value 15 R2. ~ voltage Vce is applied betweeli-the ~ase oftransistor 'lOO
and the voltage reference point (grouncl).
The carrier interruptions produce a voltage of "0" volt at the outpu-t of detector 51, w3lile the presence of the carrier resul-ts in a voltage of Vec volt. Thus, at 20every carrier interruption eapaeitor 10' is ehargecl to a voltage Vec, thereafter in the presence of -the carrier a eharge -transfer from capacitor 102 to capacitor 103 oeeurs, so that the voltage at the terminals of eapaeitor 103 will inerease by a quanti-ty whiel-l is proportional to the ratio 25C1/C2 and -to the voltage Vee. When the voltage aeross eapaeitor 103 reaehes a precletermined threshold -value this voltage is eonsidered as a logie value "1". Resis-tor 104 is ehosen so that the time eonstant R2,C~ is large relative to the period of the interruptions during -tlle validation-30sequenee S1. Tllis resistor 104 makes it possib]e to havethe validation signal deerease to the value zero after a predetermined periocl of time. As a result thereof in~er-ventions are avoide-l if during a normaL transmission of information -the validation-sequenceis irnitated. It is also 35im~ortant tl1at tlle valiclation signal l~as the predetermined duration. To ensure this it is neeessary tha-t the capaeitor 103 is well-ellarged. This implies tha-t all carrier inter-ruptions are properly reoeived ~y -the repea-ter which 1194~'~4 PHF.80-5l4 l5 16.7.S1 comprises this control circui-t 50. The importance of the use of the above-clescribed sequence SO~ will then ~e clear.
In ~'ig. 13, the gate circui-t 7l o~` control circuit 50 is formed by two inver-ters 110 and11l~ a NAND-ga-~e 112 and a NOR-gate 113. The OUtpllt of N~ND-gate 112 is connected to the input of the in-tegrating network in the forM of r--sistor 72 and capacitor 737 wilile the 01ltpUt of NOR-gate 113 is connected -to the R-input of flip-~lop 75, which itself is t`ormed by -two NAND-ga-tes 115 and 116. One input ofthe ga-tes lO 112, 113 is connected to the output of cletector 51 v~a an inverter 110; the other input of NAND-gate 112 is dir~ctly connected to the output of validation circuit 70 and the other inpu-t of NOR-gate l13 is cGnnected to the output o~
validation circuit 70 via an inverter111. In aclditioll, 15 a protection resistor 120 is provided ~etween -the ou~put of the clifferen-tiating networl~ (in the form of capacitor 76 and resistor 77) ancd the input of AND-ga-te ',~8.
In the regenerating circuits of the conven~ional type, there are often provided amplitude cletectors for the 20 signals present on tl~e path -to which the circuit is connec-ted. These regenerating circuits may also comprise a deteetor for producing a signal ~hich indicates the pre-sence of regenerated clock signals. Within the frame work of the invention it is advantageous to use either the 25 amplitude detector or the last-men~ioned presence de~ec-tor as a carrier detec-tor.
Claims (9)
1. A system of tele-locating regenerative repeaters which are included in a transmission path between two terminal stations for transmitting at a predetermined rate digital information signals in one direction by means of a forward path and in the other direction by means of a return path, one of the terminal stations comprising a tele-location transmitter for transmitting tele-location commands to the repeaters by means of the forward path, the trans-mitter comprising a regenerator for generating carrier sig-nals at the predetermined rate, a command sequence generator and an amplitude modulator for on-off modulation of said carrier signals in accordance with output signals of said command sequence generator, and each of said repeaters comprising, arranged between said forward path and said return path, a loop circuit comprising an associated control circuit and a detector, said associated control circuit coop-erating with said detector for detecting the presence of carrier signals in the forward path for receiving said tele-location commands, said command sequence generator being arranged for applying to said control circuits of said repeaters command sequences which are each formed by a pulse train having at least one pulse, which pulse train is trans-mitted by interrupting said carrier signals by means of said amplitude modulator.
2. A tele-location system as claimed in Claim 1, in which said command sequence generator is arranged to produce at least three command sequences, the first sequence having for its object to adjust said control circuits which can receive said first sequence to a valid condition, the second sequence to cause said control circuits in the valid state to establish a connection between forward and return paths by means of said loop circuit, and the third sequence to cause said control circuit which receives this third sequence to interrupt a connection between forward and return paths by means of said loop circuit, said first sequence being in the form of a pulse train having a plurality of periodic pulses the duration of which is short relative to the period, said second sequence being in the form of one pulse the duration of which is long relative to the duration of the pulses of the first sequence, said third sequence being in the form of a sequence having N pulses of a short dura-tion, N being the number of repeaters to be unlooped.
3. A tele-location system as claimed in Claim 2, wherein said command sequence generator is arranged for pro-ducing prior to said first sequence a fourth sequence having a structure which is substantially identical to the struc-ture of the third sequence.
4. A tele-location system as claimed in Claim 1, wherein in said control circuit comprises a validation cir-cuit for adjusting said control circuit to the valid state during a predetermined period of time.
5. A tele-location system as claimed in Claim 1, in which said repeaters have a blocking circuit for blocking signals to be transmitted by way of the forward path, said control circuit being arranged to cause looping of the repeater on reception of said second sequence, to cause unlooping of the repeater on reception of the first short pulse of said third sequence and, in cooperation with said blocking circuit, to cause the conversion of said first pulse of said third sequence into a pulse having a duration corresponding to the duration of the pulse of said second sequence by interrupting the transmitted carrier signals.
6. A tele-location system as claimed in Claim 5, wherein said control circuit includes a first gate which only in the valid state of the control circuit passes the signal at the output of the carrier detector to the input of an integrating network in said control circuit and to a first input of an RS-flip-flop in said control circuit, the second input of which is connected to the output of the integrating network in said control circuit, and further includes a second gate a first input of which is connected to the output of the carrier detector and a second input of which is coupled to the output of said RS flip-flop through a differentiating network in said control circuit, the out-put of said RS flip-flop being connected to a control input of the loop circuit and the output of said second gate being connected to a control input of said blocking circuit.
7. A tele-location system as claimed in Claim 4, wherein said validation circuit is formed by a pump circuit having a pnp-transistor the base of which is connected to the emitter through a diode, the emitter of which is con-nected to the output of said carrier detector through a first capacitor in said pump circuit and the collector of which is connected to a voltage reference point through the parallel arrangement of a second capacitor and a resistor in said pump circuit, the collector being the output of the pump circuit.
8. A tele-location system as claimed in Claim 1, in which the regenerator for the forward path in every repeater comprises an amplitude detector for said information signals in said forward path, wherein said carrier detector is formed by said amplitude detector.
9. A tele-location system as claimed in Claim 1, in which the regenerator for the forward path in every repeater comprises a detector for detecting the presence of regen-erated clock signals, wherein said carrier detector is formed by said presence detector.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8006061 | 1980-03-18 | ||
| FR8006061A FR2478910A1 (en) | 1980-03-18 | 1980-03-18 | REPLACER TELELOCATION SYSTEM |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1194174A true CA1194174A (en) | 1985-09-24 |
Family
ID=9239804
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000385344A Expired CA1194174A (en) | 1980-03-18 | 1981-09-08 | System for tele-locating regenerative repeaters |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4425662A (en) |
| CA (1) | CA1194174A (en) |
| DE (1) | DE3136489A1 (en) |
| FR (1) | FR2478910A1 (en) |
| GB (1) | GB2105954B (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5842328A (en) * | 1981-09-07 | 1983-03-11 | Hitachi Ltd | Controlling system for remote folding |
| FR2580880B1 (en) * | 1985-04-19 | 1992-09-04 | Cit Alcatel | REMOTE SIGNALING METHOD AND DEVICE FOR A TWO-WAY DIGITAL TRANSMISSION LINK |
| JPS61264852A (en) * | 1985-05-20 | 1986-11-22 | Fujitsu Ltd | Digital subscriber line test system |
| US4825435A (en) * | 1985-11-08 | 1989-04-25 | Digital Equipment Corp. | Multiport repeater |
| US4980887A (en) * | 1988-10-27 | 1990-12-25 | Seiscor Technologies | Digital communication apparatus and method |
| US5010544A (en) * | 1989-01-09 | 1991-04-23 | Wiltron Company | Fault location operating system with loopback |
| US5555274A (en) * | 1992-03-02 | 1996-09-10 | Teltrend Inc. | Phantom data link for digital transmission lines |
| US5680405A (en) * | 1992-09-11 | 1997-10-21 | Teltrend Incorporated | Remote reporting system for digital transmission line elements |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1485877A (en) * | 1974-01-31 | 1977-09-14 | Siemens Ag | Transmission systems |
| DE2653178B2 (en) * | 1976-11-23 | 1978-08-31 | Siemens Ag, 1000 Berlin Und 8000 Muenchen | Address-free fault location method for transmission links for digital signals |
| DE2703930C3 (en) * | 1977-01-31 | 1980-06-04 | Siemens Ag, 1000 Berlin Und 8000 Muenchen | Address-free pulse fault location for transmission links for digital signals |
-
1980
- 1980-03-18 FR FR8006061A patent/FR2478910A1/en active Granted
-
1981
- 1981-09-08 CA CA000385344A patent/CA1194174A/en not_active Expired
- 1981-09-15 US US06/302,282 patent/US4425662A/en not_active Expired - Fee Related
- 1981-09-15 DE DE19813136489 patent/DE3136489A1/en not_active Withdrawn
- 1981-09-15 GB GB08127873A patent/GB2105954B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| FR2478910A1 (en) | 1981-09-25 |
| DE3136489A1 (en) | 1983-03-31 |
| US4425662A (en) | 1984-01-10 |
| GB2105954A (en) | 1983-03-30 |
| GB2105954B (en) | 1985-06-19 |
| FR2478910B1 (en) | 1983-09-23 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |