CA1152158A

CA1152158A - Battery operated access control card

Info

Publication number: CA1152158A
Application number: CA000392383A
Authority: CA
Inventors: Thomas A. Stamm
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1981-01-14
Filing date: 1981-12-16
Publication date: 1983-08-16
Also published as: AU7845481A; US4353064A; AU542998B2; EP0056686A3; EP0056686A2

Abstract

ABSTRACT
An access control card for use in an access control system is disclosed having a battery, a wireless signal sensor such as an antenna for receiving coded wireless signals such as coded radio frequency signals generated by a card reader, a clock connected to the battery and including a receiver connected to the antenna for supplying a received signal based upon the coded radio frequency signal, a memory for storing first and second stored codes, and a transmit circuit connected to the antenna, to the clock and to the memory for comparing the first stored code to the received signal and for transmitting the second stored code when there is a match between the received signal and the first stored code.

Description

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BATTERY OPERATED ACCESS CONTROL CARD
BACKGROUND OF THE INVENTION
The present invention relates to an access control card useful in access control systems to permit access to secured areas, secured informatio~, secured systems or the like, and, more particularly, to a battery operated access control card which compareS a code generated by a card reader to a first 3tored code and, if there is a match, for transmitting a second store~d code back to the card reader to be used by the card reader to determine whether the holder of the card should be permitted to take the desired action.
Access control systems have been utilized in the past to restrict access to protected areas, information, or the like t~ only those to whom access is authorized. Such systems usually 1~ involve a card reader into which a coded card is inserted and ead. The code on the card, which may periodically be changed, may be i~entica~ ~for all those wishing to have access;
Alternatively, each person who is~authorized to have acress may be assigned h;s own personal code which agaln may be periodically 20~ changed.~ Upon the recognitlon of~a perm;issible code, the card r~eader and associated system wlll~permit access.
These c~ard readers usually ~ ~c~ompr ise a cabinet for : hoaslng the ~ access control system~ o~ subsys~em thereof and typlcally have a~ plurallty of sensing fingers for makin~ contact-25~ ~with ~he cards~lnserted into the reader and for sensing the codeon the~ card t~ allow access if~the card carrier has the proper cod~e. To gain access, the card is inserted into a slot in the cablnet which results in the wiping over of the surface of the card by the sensing~fingers during both this insertion and the 9ubsequent wit~d~awal of the card.
Because these typical pr ior art card readers involve ..
con~act between the reader and the card, there is substanti31 , ~ .

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wear and tear on both the reader and the card which adversely affects the reliability of the overall system. Moreover, since there is direct contact between the reader and the card, and since card readers used in access control systems are quite often located outdoors, certain elements of the card reader, notably the sensing fingers, are exposed to the vagaries of weather and are, therefore, subject to corrosion which again adversely affects the reliability of the system.
The prior art has attempted to solve many of these problems by providing passive cards which either load down a magnetic field which can be then sensed by the generator of the magnetic field to permit access or to receive an RF transmission~
code it and return it to the generator of the RF signal to be decoded. An example of this latter approach can be found in Unlted States Patent 4,210,900 which shows a surface acoustic wave device for receiving an RF generated signal and for transmitting a coded RF signal in response thereto to a card reader. However, the body capacitance of the users of many types of these passive devices tends to ground the signals being transmitted by the reader so that no useful signal is returned to the reader and access will not be permitted. Patent 4,210,900 shows one way around this problem by providing a card which can be inserted into a reader but which does not require physical contact with any part of the reader and in which the sensing elements of the reader can be sealed from exposure.
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SUMMARY OF THE INVENTION
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The card according to the present invention offers an improved alternative solution by providing a card having a battery, an antenna arrangement for receiving coded wireless signals generated by a card reader, a clock circuit connected to the battery and including a receiver connected to the antenna for supplying a received signal based upon the coded wireless signal, ~

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a memory for storing first and second stored codes, and a transmit circuit connected to the antenna arrang~ment! to the clock circuit and to the me~ory for comparing the first stored code and the received signal and for transmitting the second stored code when there is a match between the received signal and the first stored code.
Since the card has a power supply in the form of a battery located thereon, the si~nal strength may be maintained such that a useful signal can be transmitted from the card to the reader. Thus, the card need not be inserted into a card reader.
; There is no actual physical contact between the card ana the reader and the card may instead be kept in the pocket or worn as a badge.
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BRIEF DESCRIPTION OF THE DR~AWINGS
These and other features and advantages will become more apparent from a detailed consideration of the invention when taken in conjunctio~ w-ith the drawings in which Figure 1 shows a card according to the present inven :, ~
; : tlon~with the battery and circult elemen-:;locaied the~eon

2~0~ :Figure 2 show~s a block~diagr~am for the. circuit on the ca~d shown in Figure l;

: : Figures 3A and 3B:show the antenna and clockjreceiver . clrcuit~shown in~block form in: Pigure 2 , ~
~ igure 4 shows~ the memory~shown in block form in ~ as ~lgur~e 2;
:; : Figure 5:shows the transmit~circuit shown in block form in~Figure 2;: and, ~ . ~

Figures ~6A and 6B 5how the timing diagrams for the cir~uits~shown:in Figures:3A 5.

~ - , : ~ 30 : ~ DETAILED DES~RIPTIQN

~: : Access control card 10 shown in Figure 1 may have a ~:~ subbase 12 made of z suita~e plastic or similar material for ' ' . , .

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holding the battery and circuit elements of the card. Although the card can receive any type of wireless transmission from a transmitter such as ultrasonic, infrared, etc., the preferred embodiment according to the present invention uses RF transmis-sions; Accordinqly, antenna 11 (which may be any other type ofwireless signal se~sing means depending upon the form of.energy used in the transmission) is wound in loop form around the periphery of card 12 and is connected to a printed circuit type board 13 located in the center of card 12. The printed circuit board 13 supports battery 14 which forms the power source for access control card 10 and may he a lithium battery or small size and long life. In addition, circuit elements 15-18 are `~ located on printed circuit board 13 and may comprise the capacitors and resistors of the card mounted system. Chip 19 may lS compxise the logic gates, latches, fl ip-flops and counters which form the rest of the system mounted on access control card 10.
Thë block diagram of the system mounted on access control card 10 is snown in Figure 2. Each block contains the ~name of the function for the block and~ the correspon~ing figure 20 number of the figure showing the details of the block. Broadly, the system mounted~on access control card lQ comprises an antenna 11 which is used ~for receiving ~the radio frequency r?r.erated signal from a card rea~der and to transmit the access control card code (second stored code) back to the reader or verification.
~25~. Although antenna 11 may comprise an ant?nna for receiving the signal transmitted by the card reader and a separate antenna for tran~mitting the card code back to the card reader, in the preferred embodiment it compr ises the single loop 11 wound around the per iphery of the card .
The signal received by antenna 11 is ~ransmit~ed to clock/receiver ~ircu~ 20. In circuit 20t the receive circuit initializes the operation of a clock which then controls the - ~5~LS~

overall functioning of the system mounted on access control card 10. Specifically, the clock in clock/receiver 20 clocks memory 50 to supply a first coded signal to transmit circuit 80. The receiver portion of clock/receiver 20 supplies the received signal or a received signal based upon the radio frequency signal received by antenna ll to transmit circuit 80. Transmit circuit 80 compares the first coded signal with the received signal.
If these two signals match, the clock continues to drive memory 50 to then supply the second coded signal to transmit circuit 80 which then supplies this second coded signal as a transmit signal to antenna ll for transmisslon back to the card reader. However, if there is a mismatch between the first coded signal and the received signal, then the second coded signal is not supplied by transmit 80 as a transmit signal to the antenna ll.
,As shown in Figure 6A, the coded radio frequency signal, which is connected through as a received signal, com-prises a continuous carrier signal 101 terminated by a start bit 102 and a series of 16 data bits 103. The clock shown 1n Figure 3B synchronizes to the trailing edge of the carrier, skips the start bit space and then begins addressing memory 50 shown in .
;~Figure 4~ Antenna ll is shown in Figure 3A which also shows the .
receiver portion of clock/recelver 20.~ Antenna 11 receives the R~ transmission from the card~ reader and supplies this signal through amplifiers 5 and 6 to switch 7 which acts as a charge and discharge control for capacitor 8. The charge across the capacitor is then connected through inverter 9 and provides the received signal shown in Figure 6A.

Since it is desired to save battery energy, a switch is provided between the battery and the amplifier sections 5 and 6 of the receiver. The switch periodically allows the receiver to sample for transmission from the card reader. Any received ~ -5-:

~L5~S8 signal as supplied to output line 22 by inverter 9 is then used as a reset on counter 21 to lock on stages 5 and 6 for reception.
This allows the card reader to, for example, permit access only after a predetermined number of transmissions, while minimizing waiting time for card receiver activation. Thus, switch ~5 is connected between the battery and amplifier sections 5 and 6.
Switch 25 is controlled by a timing circuit comprising an astable multivibrator 23 providing the clock signal to counter 21.
Decoder 24 decodes the Q5-Q7 counter outputs and operates as shown to control switch 25~
The output from inverter 9, i.e. the received signal, is connected to the C input of flip-flop 26 for providing the CK
START and the CK START signals. The CK START signal is shown in Figure 6A and the CK START signal is merely the inversion of the CK START signal. The leading edge of the carrier signal causes flip-flop 26 to switch which drives its Q output high and its Q
output low. When the Q output is driven high, flip-flop 27 is likewise switched to drive its Q output high and its Q output low. When the Q output of ~lip-flop 27 is driven high the CLOCX
ENABLE output is driven high for allowing oscillator 31 of the clock circuit shown in Figure 3B to begin providing clock pulses.
It is to be noted that the trailing edge of each pulse in the received signal will reset flip-flop 26 through inverter 28 and OR gate 29 and that each leading edge will switch flip-flop 26 to ~ that the CX START output will be a series of pulses matched to the pulses of the received signal and the CK START signal will be the inversion of these pulses. However, flip-flop 27 is only reset by the CLOCR RESET signal and as long as the CLOCK RESET
signal does not change, flip-flop 27 will switch once and remain in its switched condition as shown by the CLOCK ENABLE signal of Figure 6A. Also, when the carrier signal 101 goes low, the CK
START signal causes flip-flop 32 (Figure 3B) to switch driving ~15Z~5~

the COUNTERS RESET signal low, synchronizing timing for all subsequent operations.
Oscillator 31 is a crystal based oscillator providing, for example, a 330K Hz output signal which is used for providing the timing of the access control card. Oscillator 31 drives counter 33 which has its Ql output connected to the C terminal of flip-flop 34 and its Q2-Q7 terminals coupled through decoder 35 to the D terminal of flip-flop 34. Flip-flop 34 thus provides the STROBE signal as shown in Figure 6A and the STROBE signal which is an inversion of STROBE. In addition, output Q7 of counter 33 provides the 2500 ~z CLOCK signal and the 2500 Hz CLOCK signal through inverter 36. As further shown in Figure 3B, the 2500 Hz CLOCK signal is connected to the C terminal of flip-flop 41 which is used to enable AND gate 42 to pass the 2500 Hz CLOCK signal to the ADDRESS CLOCK output. Flip-flop 41 is used to delay the clock by 1 bit space.
The START BIT DELAY provided by the Q output of flip-flop 41 in Figure 3B is used to trigger flip-flop 51 shown in Figure 4 to ènable memory chip 52. At the same time, the ADDRESS CLOCK signal drives counter 53 for providing the addresses to memory chip 52O Counter 53 addresses first those locations in memory chip 52 in which a first coded signal corresponding to the RECEIVED SIGNAL are stored. Memory chip 52 will, in response to the addresses supplied by counter 53, transmit out this first coded signal over its output terminal .
D
out The first coded signal supplied out over the DATA OUT
line fr~om memory chip 52 is supplied to one input of the comparator circuit in the ~orm of EXCLUSIVE OR gate 81 shown in Figure 5. The first coded signal is supplied at the same rate as the RECEIVED SIGNAL and as long as the first coded signal matches the RECEIVED SIGNAL bit for bit, the output level from EXCLUSIVE

, ~S2~lS8 OR gate 81 will not change. At the end of the receive sequence, address line A4 to memory chip 52 goes high which causes the output from NOR gate 55 to go low and results in a high output from inverter 56. This high output indicates the transmit mode for battery access control card 10 and enables NAND gate 57 to begin passing the second coded signal supplied by memory chip 52.
Since a third input to NAND gate 57 is connected to the read/write input R/W, NAND gate 57 will only pass the second code out during the read operation. NOR gate 55 decodes the A4 and A5 address lines which, as shown in Figure 6B insures that the transmit mode signal will remain high during the entire transmit mode.
The second coded signal is supplied over the transmit enable line to a corresponding input to flip-flop 82 shown in 15 Figure 5. Flip-flop 82 is configured along with fllp-flop 83 to supply the second coded signal through transistor 84 as the ~ .
TRANSMIT SIGNAL which is connected back through Figure 3A to antenna 11. At the end of the transmission cycle, AND gate 61 ; decodes address lines A2 and A6 for providing the END OF CYCLE

signal which is connected back to OR gate 45 for providing the CLOCK RESET signal to flip-flop 27 which resets flip--flop 27 and thereby disables the clock shown in Figure 3B and the operation ,, is terminated. Also, when the C~OCK ENABLE signal goes high, flip-flop 32 of Figure 3B is reset for providing the COUNTER
25 RESET signal to reset counter 33, flip-flop 34, counter 53, and flip-flop 51 for disabling memory chip 52. Thus, the circui~ is now in a condition for receiving a new transmission from the card reader.

If during the receive mode there had not been a match between corresponding bits of the RECEIVED SIGNAL and the first coded signal as compared by EXCLUSIVE OR gate 81, the output of EXCLUSIVE OR gate 81 will go high for switching flip-flop 86 upon ~r 5~

the next 2500 HZ CLOCK pulse. When flip-flop 86 switches, flip-flop 87 will switch upon receiving the next STROBE pulse.
Flip-flops 86 and 87 are designed to delay the MISMATCH signal until the STROBE output goes low. The DELAYED MISMATCH signal is then supplied to OR gate 45 of Figure 3A for resetting flip-flop 27 and thereby resetting all of the other counters and flip-flops of the circuit through flip-flop 32 and its output COUNTERS
RESET. As will be understood, the DELAYED MISMATCH signal can be provided at any time beginning with the first bit of the RECEIVED
10 SIGNAL and including the last bit of the RECEIVED SIGNAL. If a DELAYED MISMATCH signal is received, the operation of the clock shown in Figure 3B will be terminated before the clock begins the addressing sequence of memory chip 52 for supplying the second coded signal to the transmit circuit shown in Figure 5.
In Figure 4, a PROGRAM inpuk is used for storing ne~
codes in memory chip 52. When the PROGRAM input goes low, memory chip 52 is enabled for a write operation and will write into memory a RECEIVED SIGNAL received at its Din input.

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Claims

The embodiments of the invention in which an exclusive property or right is claimed are defined as follows:

1. An access control card used in access control systems comprising:
a battery;
wireless signal receiving means for receiving a coded wireless signal generated by a card reader;
clock means connected to the battery and including a receiver connected to the antenna for supplying a received signal based upon said coded wireless signal;
memory means for storing first and second stored codes;
and, transmit means connected to said wireless signal receiving means, to said clock means and to said memory means for comparing said first stored code and said received signal and for transmitting said second stored code when there is a match between said received signal and said first stored code.

2. The card of claim 1 wherein said transmit means com-prises comparator means for providing a mismatch signal when said received signal and said first stored code do not match, and said clock means comprises a clock and clock enable means responsive to said mismatch signal for terminating operation of said clock.

3. The card of claim 2 wherein said memory means comprises a counter responsive to said clock for providing addresses and a memory circuit responsive to said addresses for supplying said first stored code to said comparator means, said clock continuing to drive said address counter if said received signal has been successfully compared to said first stored code and for interrupting said counter if said first stored code is not successfully compared to said received signal.

4. The card of claim 3 wherein said counter has a plurali-ty of outputs and said memory means further comprises a decoder circuit for decoding selected outputs of said counter for enabling said transmit means to transmit said second stored code only during a transmit mode, said transmit mode only occurring after the first stored code has been compared to the received signal.

5. The card of claim 4 wherein said memory means comprises an end of cycle decoder connected to selected outputs of said counter for providing an end of cycle signal after said second stored code has been supplied by said memory means to said transmit means, said end of cycle signal resetting said clock enable means to interrupt said clock.

6. The card of claim 5 wherein said clock comprises an oscillator responsive to said clock enable means for providing an output and a counter-decoder circuit responsive to said output from said oscillator to drive said counter of said address means.

7. The card of claim 6 wherein said clock enable means comprises flip-flop means responsive to the beginning of said received signal for energizing said clock and responsive to said end of cycle signal and said mismatch signal for terminating operation of said clock.

8. The card of claim 1 wherein said memory means comprises a counter responsive to said clock means for providing addresses and a memory circuit responsive to said addresses for supplying said first stored code to said transmit means, said clock means continuing to drive said address counter if said received signal and said first stored code have been successfully compared by said transmit means and for interrupting said address counter if said first stored code is not successfully compared to said received signal.

9. The card of claim 8 wherein said counter has a plurali-ty of outputs and said memory means further comprises a decoder circuit for decoding selective outputs of said address counter for enabling said transmit means to transmit said second stored code only during a transmit mode, said transmit mode only occurring after the first stored code has been compared to the received signal.

10. The card of claim 9 wherein said memory means comprises an end of cycle decoder connected to selected outputs for said counter for providing an end of cycle signal after said second stored code has been supplied by said memory means to said transmit means, said end of cycle signal resetting said clock means to interrupt said clock means.

11. The card of claim 10 wherein said clock means comprises an oscillator for providing an output and a counter-decoder circuit responsive to said output from said oscillator to drive said counter of said address means.

12. The card of claim 1 wherein said memory means comprises a counter driven by said clock means and having a plurality of outputs, and a decoder circuit for decoding selected outputs of said counter for enabling said transmit means to transmit said second stored code only during a transmit mode, said transmit mode only occurring after the first stored code and said received signal have been compared by said transmit means.

13. The card of claim 12 wherein said memory m means com-prises an end of cycle decoder connected to selected outputs from said counter for providing an end of cycle signal after said second stored code has been supplied by said memory means to said transmit means, said end of cycle signal resetting said clock means to interrupt said clock means.

14. The card of claim 13 wherein said clock means comprises an oscillator for providing an output and a counter-decoder circuit responsive to said output from said oscillator to drive said counter of said address means.

15. The card of claim 1 wherein said wireless signal receiving means comprises an antenna and said coded wireless signal comprises a coded radio frequency signal.

16. The card of claim 15 wherein said transmit means comprises comparator means for providing a mismatch signal when said received signal and said first stored code do not match, and said clock means comprises a clock and clock enable means responsive to said mismatch signal for terminating operation of said clock.

17. The card of claim 16 wherein said memory means com-prises a counter responsive to said clock for providing addresses and a memory circuit responsive to said addresses for supplying said first stored code to said comparator means, said clock continuing to drive said address counter if said received signal has been successfully compared to said first stored code and for interrupting said counter if said first stored code is not successfully compared to said received signal.

18. The card of claim 17 wherein said counter has a plurality of outputs and said memory means further comprises a decoder circuit for decoding selected outputs of said counter for enabling said transmit means to transmit said second stored code only during a transmit mode, said transmit mode only occurring after the first stored code has been compared to the received signal.

19. The card of claim 18 wherein said memory means com-prises an end of cycle decoder connected to selected outputs of said 'counter for providing an end of cycle signal after said second stored code has been supplied by said memory means to said transmit means, said end of cycle signal resettinq said clock enable means to interrupt said clock.

20. The card of claim 19 wherein said clock comprises an oscillator responsive to said clock enable means for providing an output and a counter-decoder circuit responsive to said output from said oscillator to drive said counter of said address means.

21. The card of claim 20 wherein said clock enable means comprises flip-flop means responsive to the beginning of said received signal for energizing said clock and responsive to said end of cycle signal and said mismatch signal for terminating operation of said clock.

22. The card of claim 15 wherein said memory means com-prises a counter responsive to said clock means for providing addresses and a memory circuit responsive to said addresses for supplying said first stored code to said transmit means, said clock means continuing to drive said address counter if said received signal and said first stored code have been successfully compared by said transmit means and for interrupting said address counter if said first stored code is not successfully compared to said received signal.
said received signal.

23. The card of claim 22 wherein said counter has a plurality of outputs and said memory means further comprises a decoder circuit for decoding selective outputs of said address counter for enabling said transmit means to transmit said second stored code only during a transmit mode, said transmit mode only occurring after the first stored code has been compared to the received signal.

24. The card of claim 23 wherein said memory means com-prises an end of cycle decoder connected to selected outputs for said counter for providing an end of cycle signal after said second stored code has been supplied by said memory means to said transmit means, said end of cycle signal resetting said clock means to interrupt said clock means.

25. The card of claim 24 wherein said clock means comprises an oscillator for providing an output and a counter-decoder circuit responsive to said output from said oscillator to drive said counter of said address means.

26. The card of claim 15 wherein said memory means com-prises a counter driven by said clock means and having a plurality of outputs, and a decoder circuit for decoding selected outputs of said counter for enabling said transmit means to transmit said second stored code only during a transmit mode, said transmit mode only occurring after the first stored code and said received signal have been compared by said transmit means.

27. The card of claim 26 wherein said memory means com-prises an end of cycle decoder connected to selected outputs from said counter for providing an end of cycle signal after said second stored code has been supplied by said memory means to said transmit means, said end of cycle signal resetting said clock means to interrupt said clock means.

28. The card of claim 27 wherein said clock means comprises an oscillator for providing an output and a counter-decoder circuit responsive to said output from said oscillator to drive said counter of said address means.

29. An access control card used in access control systems comprising:
a battery;
an antenna for receiving a coded radio frequency signal generated by a card reader;
a receiver connected to said antenna and to said battery for supplying a received signal based upon said coded radio frequency signal;
a clock connected to said receiver and to said battery for supplying a clock signal upon receipt by the receiver of said coded radio frequency signal;
memory means connected to said clock for storing first and second stored codes and for supplying said first and second stored codes to an output of said memory means in response to said clock signal;
comparator means connected to said output of said .. memory means and connected to said receiver for comparing said first stored code to said received signal and connected to said clock means for terminating said clock signal when there is a mismatch between said first stored code and said received signal; and, transmit means connected to said antenna, to said clock means and to said memory means for transmitting said second stored code after said first stored code has been successfully compared to said re-ceived signal.

30. The card of claim 29 wherein said clock means comprises a clock and clock enable means responsive to said comparator means for terminating operation of said clock when there is a mismatch between said first stored code and said received signal.

31. The card of claim 30 wherein said memory means com-prises a counter responsive to said clock for providing addresses and a memory circuit responsive to said addresses for supplying said first stored code to said comparator means, said clock continuing to drive said counter if said received signal has been successfully compared to said first stored code and for interrupting said counter if said first stored code. is not successfully compared to said received signal.

32. The card of claim 31 wherein said counter has a plurality of outputs and said memory means further comprises a decoder circuit for decoding selected outputs of said counter for enabling said transmit means to transmit said second stored code only during a transmit mode, said transmit mode only occurring after the first stored code has been compared to the received signal.
.

33. The card of claim 32 wherein said memory means com-prises an end of cycle decoder connected to selected outputs of said counter for providing an end of cycle signal after said second stored code has been supplied by said memory means to said transmit means, said end of cycle signal resetting said clock enable means to interrupt said clock.
.

34. The card of claim 29 wherein said memory means com-prises a counter responsive to said clock means for providing addresses and a memory circuit responsive to said addresses for supplying said first stored code to said comparator means, said clock means continuing to drive said counter if said received signal has been successfully compared to said first stored code and for interrupting said counter if said first stored code signal is not successfully compared to said received signal.

35. The card of claim 34 wherein said counter has a plurality of outputs and said memory means further comprises a decoder circuit for decoding selected outputs of said counter. for enabling said transmit means to transmit said second stored code only during a transmit mode, said transmit mode only occurring after the first stored code has been compared to the received signal.

36. The card of claim 35 wherein said memory means com-prises an end of cycle decoder connected to selected outputs from said counter for providing an end of cycle signal after said second stored code has been supplied by said memory means to said transmit means, said end of cycle signal resetting said clock means to interrupt said clock means.

37. The card of claim 29 wherein said memory means com-prises a counter driven by said clock means and having a plurality of outputs, and a decoder circuit for decoding selected outputs of said counter for enabling said transmit means to transmit said second stored code only during a transmit mode, said transmit mode only occurring after the first stored code has been compared to the received signal.

38. The card of claim 37 wherein said memory means com-prises an end of cycle decoder connected to selected outputs from said counter for: providing an end of cycle signal after said second stored code has been supplied by said memory means to said transmit means, said end of cycle signal resetting said clock ; means to interrupt said clock means.