US3631433A

US3631433A - Detection and alarm system

Info

Publication number: US3631433A
Application number: US857882A
Authority: US
Inventors: Keith M Dix
Original assignee: FIRE PROTECTION CO
Current assignee: FIRE PROTECTION CO
Priority date: 1969-09-15
Filing date: 1969-09-15
Publication date: 1971-12-28
Anticipated expiration: 1988-12-28

Abstract

A fire detection and alarm system for sensing a dangerous fire or like condition in one part of a building or the like and providing an alarm signal at a remote location in the building, by means of high-frequency carrier signals superimposed on the existing wiring, including a fire detection transmitter for sensing fire and transmitting at one frequency, a receiver responsive to signals from the fire transmitter for actuating an alarm, a normally energized supervisory transmitter adjacent the fire-detecting transmitter and operative at a second frequency for sensing circuit failure, and a supervisory receiver at the remote location responsive to signals from the supervisory transmitter for actuating an alarm on power failure when the supervisory transmitter stops sending. In an alternative embodiment for use in a large building involving many different widespread areas, a separate fire detection transmitter is provided in each area in association with a stepping relay which identifies the area, and an annunciator at the remote alarm location includes a single stepping relay for selectively energizing indicators not only warning of fire or the like but also showing the location.

Description

United States Patent [72] lnventor Keith M. Dix

Bannockburn, Ill.

[21] Appl. No. 857,882

[22] Filed Sept. 15, 1969 [45] Patented Dec. 28, 1971 [73] Assignee Fire Protection Company [54] DETECTION AND ALARM SYSTEM 23 Claims, 5 Drawing Figs.

[52] US. Cl 340/216, 340/164 A, 340/168 A, 340/409, 340/416 [51] Int. Cl G081) l/08 [50] Field of Search 340/164,

Primary ExaminerJohn W. Caldwell Assistant Examiner- David L. Trafton Attorney-Hofgren, Wegner, Allen, Stellman & McCord ABSTRACT: A fire detection and alarm system for sensing a dangerous fire or like condition in one part of a building or the like and providing an alarm signal at a remote location in the building, by means of high-frequency carrier signals superimposed on the existing wiring, including a fire detection transmitter for sensing fire and transmitting at one frequency, a receiver responsive to signals from the fire transmitter for actuating an alarm, a normally energized supervisory transmitter adjacent the fire-detecting transmitter and operative at a second frequency for sensing circuit failure, and a supervisory receiver at the remote location responsive to signals from the supervisory transmitter for actuating an alarm on power failure when the supervisory transmitter stops sending.

In an alternative embodiment for use in a large building in- [56] Rderences Cited volving many different widespread areas, a separate fire detec- UNITED STATES PATENTS tion transmitter is provided in each area in association with a 1,139,632 5/1915 Booth 340/164 stepping relay which identifies the area, and an annunciator at 1,662,877 3/1928 Almquist.. 340/164 X the remote alarm location includes a single stepping relay for 2,567,908 9/1951 Levy 340/216 X selectively energizing indicators not only warning of fire or the 2,944,251 7/1960 Tethrow 340/409 like but also showing the location.

B L 234 SUPE'QV/SORY 174 256 253 lefc.

E4 j 7 6 15 I I 9 ll/91PM /1 177 0 l 9/ PULSE COIL 0 53/ Z00 o V v IPFJEI'CO/L gg --Z5Z Patented Dec. 28, 1.971

3 Sheets-Sheet 1 Patented Dec. 28, 1971 3 Sheets-Sheet 2 I 1 A J 2 wml w .wm kw W m 3 K H J% mm JJNN Patented Dec. 28, 1971 3 Sheets-Sheet 5 DETECTION AND ALARM SYSTEM SUMMARY OF THE INVENTION In the past, there have been detection and alarm systems devised for use in connection with protection of premises such as personal residences and industrial property against such adversities as fire and undesirable intrusion. Usually, such systems involve the use of detection means for sensing fire, intrusion or the like at one or more locations on the protection property together with means at some convenient location, usually remote from the detection zone, for indicating detection of the undesirable condition. The detection means may take the form of visible or audible indicators, or both, which attract attention and advise of the need for taking appropriate action.

In view of the separation of the detection zone or zones by some distance from the place where an alarm is sounded, there arises the need for transmitting signals from one place to another. In some of the prior art devices, there is a requirement for installation of extensive wiring reaching from one or more detection places to one or more places for indicating the trouble. Installation of entire wiring systems involves substantial expense and inconvenience in existing structures, as a result of which it is desirable if installation of additional wiring can be avoided. According to the present invention, a detection and alarm system is provided for detecting and indicating fire or the like and adapted to make use of existing wiring in a building or the like for transmission of signals at carrier frequencies, usually relatively high, over the wiring usually already in place in existing structures for the purpose of providing the conventional 60 cycle 110 volt power. In a preferred form of the invention a detecting and transmitting device may be housed in a relatively small hand-sized casing adapted to be installed adjacent an existing wall receptacle, including a plug adapted to register with the receptacle for purposes of providing power supply to the transmitter and for the purposes of superimposing carrier frequencies on the existing wiring. Similarly, a receiving and indicating device may be housed in a small container adapted to be utilized at a remote location adjacent another wall receptacle, where the receiving device may be plugged into the receptacle for power supply and for receiving the carrier signals.

In systems of the character under consideration, where elec trical systems are utilized, it is desirable to maintain some form of supervision over the detecting and indicating system in order to determine that it is at all times in operative condition and ready to perform in event of the rare occurrence of the emergency condition against which protection is to be afforded. In accordance with the present invention, use is made of a supervisory transmitter employed adjacent the fire alarm transmitter. Where the fire alarm transmitter is normally deenergized and inactive except in case of emergency, the supervisory transmitter is supplied with power from a similar source and is normally energized and transmitting to a supervisory receiver in the vicinity of the alarm receiver and the arrangement is such that if the power supply fails, the supervisory transmitter stops transmitting and the supervisory receiver stops receiving, at which time the latter closes a switch in circuit with a battery source for energizing a trouble indicator to advise of problems in the circuitry. Such an arrangement is constructed to indicate power failure at either the supervisory transmitter or the supervisory receiver, and these are respectively adjacent the alarm transmitter and the alarm receiver. If desired, the supervisory transmitter may be conveniently packaged with the alarm transmitter and the supervisory receiver may be packaged with the alarm receiver.

In the preferred circuitry, both transmitters are energized through relay-controlled contacts. The relay coils are connected in series with each other, with one or more detection switches and with a power supply provided by the existing wiring. Supervision of the extended part of the detecting circuitry is provided by means of a relatively large resistance at the end of the line in parallel with one or more detection switches, and

the supervisory relay coil is a low-current coil nonnally energized when the resistance is in the circuit, while the alarm relay coil is a high-current coil which is only energized when one of the detection switches is closed to bypass the resistance.

In a second embodiment, the supervisory control is utilized in connection with a system adapted for use in an industrial installation or other large building where many widely separated detection areas are included. In installations of this type, it is important not only to signal the occurrence of fire or other trouble, but also to indicate the location of the problem in order to know at once where to take appropriate action. In the past, in multiple area detection systems, identity as to the location of the area where trouble occurs has sometimes been provided by utilizing transmitters and receivers for each of the difi'erent areas operating at different frequencies, but this involves a substantial expense where transmitters and receivers are provided for each zone. Alternatively, prior art devices have made use of transmitters for sending codes which have the object of identifying the source of trouble, but the codes are complex where many areas are involved and they often require extensive memorization of the codes in order to identify the signals.

According to the present invention, each of the detection zones includes a stepping relay which may be structurally similar to the remainder of the relays so that a movable contact is adapted to move past a plurality of stationary contacts. In each area, a different stationary contact is wired to interrupt the relay. In reaching the interrupted position, each relay sends a number of identifying signals peculiar to its location.

At the indicating station, a single relay includes a movable contact adapted to sweep past a plurality of stationary contacts each having an indicating device identifying a different protection zone. Thus, each transmitter sends a number of signals peculiar to its location and the receiver identifies the source of trouble by the number of signals received.

DRAWINGS FIG. 1 is a wiring diagram illustrating a combined fire alarm transmitter and supervisory transmitter according to the present invention;

FIG. 2 is a wiring diagram illustrating a supervisory receiver used with the transmitter of FIG. 1;

FIG. 3 is a wiring diagram illustrating an alarm receiver used with the transmitter of FIG. 1;

FIG. 4 is a diagram illustrating another embodiment including a combined alarm and supervisory transmission system for use in one of the protected zones in a large industrial installation according to the present invention; and

FIG. 5 is a diagram illustrating an alarm and supervisory receiving system for use with the transmission system of FIG. 4.

DETAILED DESCRIPTION Referring now to FIG. 1 in more detail, a combined alarm and supervisory transmitter includes two similar transmitting channels, one designated 10 for transmitting alarm signals at a frequency on the order of kc., for example, and one designated 11 for transmitting supervisory signals at a frequency on the order of kc., for example. The transmitting circuitry is adapted to be housed in a relatively small container on the order of 2 inches X 6 inches X 8 inches, for example. The two

transmitting channels

10 and 11 are adapted to be supplied from a common source such as the existing wiring in a home or the like by means of a plug 13 adapted to be inserted in a wall receptacle to supply the primary winding of a transformer 15. The 60 cycle supply is converted to 12 volt DC in a full wave rectifier including the secondary of transformer 15, a pair of diodes 16.and 17 and a polarized capacitor 19.

The positive DC signal from either end of the secondary winding of the transformer 15 is supplied to both transmission channels. In the alarm channel 10, the positive signal is applied to the emitter of transistor 22 through a biasing network including capacitor 23 and resistance 25. The base of the transistor 22 has a positive DC bias voltage applied to it at the junction of a voltage

divider including resistances

27 and 28. The base-emitter circuit includes a series capacitor 30 and a portion of inductor 32 which has a common core with the collector output circuit 33 and a trap circuit 35. Since the collector circuit and the base circuit are coupled together through the common core of the inductor 32, the necessary feedback conditions exist and the transistor 22 functions as an oscillator. The oscillating signal developed at the collector is coupled to an output including transformer secondary 36 which is serially connected through

capacitors

37 and 38 to the input circuit at opposite ends of the primary of the transformer 15 as by means of wires 39 and 40. The oscillator frequency, for example 80 kc., is therefore impressed upon the existing distribution system in the home or the like and. may be transmitted to an alarm receiver as described hereinbelow. The channel is adapted to transmit when normally open switch contacts 1ATR2 in circuit with capacitor 30 are closed in a manner described below.

It will be seen that transmitter channel 11 is substantially identical with channel 10 as a result of which the description will not be repeated. The component parts are identified by like reference numbers with prime sufiixes, except that channel 11 is adapted to transmit upon closure of normally open switch contacts ISTRZ. It should be understood that the

transmitter channels

10 and 11 together with power supply are substantially conventional and may be obtained commercially.

In the alarm transmitter channel 10, the switch contacts 1ATR2 are relay controlled by means including a coil IATR which is connected in circuit with the secondary of transformer by

means including wires

42 and 44. In transmitter channel 11, the switch contacts ISTRZ are relay controlled by means including a winding ISTR in series circuit with the winding IATR. The two relay coils in turn are wired in series with one or more detection switches as at 45, connected in parallel with each other across the

wires

42 and 44. The detection switches 45 may take any conventional form such as wellknown fire detection switches, or smoke detection switches, or intrusion switches, or in some instances it may even be desirable to provide manually actuable switches. In parallel with the switches 45 at the end of the extended detection circuit, there is a relatively high-resistance 47 connected across the

wires

42 and 44. In the alarm illustrated, the supervisory relay coil lSTR is a low-current coil which is energized across the resistance 47 when the switches 45 are open. On the other hand, the alarm relay coil lATR is a high-current relay which is only energized when one of the switches 45 is closed to bypass the resistance 47. Thus, with the alarm shown, when the plug 13 is connected with the existing wiring, supplying power to the transmitter channels, the relay coil lSTR is normally continuously energized, closing the contacts ISTR2 so that the transmitter channel 11 is transmitting at its frequency of I40 kc., for example.

At the same time, the energized coil lSTR also opens its nonnally closed contacts IATRI in circuit with a local supervisory alarm including an audible device 48 and a visible lamp 49 connected across a 6-volt battery 50. The battery 50 is normally trickle charged by means of a transformer 52 connected across input leads 13a and 1311 from the plug 13, and a rectifier in circuit with the secondary of transformer 52, including diodes 54 and 55, and a resistor 57. So long as the power supply at 13 continues, and the integrity of the

detection system

42,44 remains intact, the coil lSTR remains energized, the contacts ISTRl remain open and the indicators 48 and 49 remain deenergized. In the event of loss of power at 13, or damage in the

detection system

42,44, the coil ISTR is deenergized, the contacts lSTRl are closed and the battery energizes the audible indicator 48 and the visible indicator 49. It it is desirable to disable the audible indicator 58, a manually operable switch 59 may be opened to discontinue the noise while the lamp remains illuminated. In order to facilitate shipment without discharging the battery 50, the indicator circuit may include a pin-operated switch 60 adapted to be closed when the system is put in use by withdrawing a manually accessible pin.

In order to provide a local alarm in the event of fire or intrusion, the alarm relay lATR includes normally open switch contacts lATRI in circuit with an audible indicator 62 and a visible lamp 63 connected across the input leads 13a and 13b. When the coil IATR is energized, the contacts IATRl are closed to energize the indicators 62 and 63.

In order to restore the transmission system to normal in the event the alarm relay lATR has been energized, a manual reset switch 61 is provided in circuit with the coil and adapted to be opened to deenergize both coils on putting the system into service again.

Referring now to the supervisory receiver illustrated in FIG. 2, a plug 65 is adapted to be inserted into a wall receptacle in the existing wiring in a home or the like at a location remote from the transmitter illustrated in FIG. 1. The supervisory receiver includes leads 65a and 65b from the plug 65 to the primary of a transformer 67 which has a secondary in circuit with a full wave

rectifier including diodes

68 and 69 and capacitor 70. Through a wire as at 72, the DC power supply maintains the emitters of a transistor 73 and a transistor 74 at a positive potential on the order of 12 volts. The bias is applied to the emitter of transistor 74 through a resistancecapacitance biasing network including resistance 75 and capacitance 76. The secondary of transformer 67 includes a center tap 77 which is connected through a relay coil SRR to the collector of transistor 73. The center tap is connected through coil limiting resistor 78 to one end of a tank circuit including inductor 80 and capacitor 81. A center tap 82 on the inductor 80 is connected to the collector of transistor 74. A smoothing capacitance 83 is connected across the DC supply.

On transmission by the supervisory transmitter channel of FIG. 1, the signals received at the supervisory receiver of FIG. 2 through the plug 65 are transmitted by wires 84 and 85 through

capacitors

87 and 88 to the primary of a transformer 90 including a secondary providing the inductance in the first of two stages of a parallel resonant circuit which selectively provides a high-voltage signal output from the primary of transformer 92 of the second stage of the resonant circuit. Such signal is coupled to the secondary of transformer 92 in the base circuit of transistor 74, which may be a standard tuned collector PNP-amplifier. The base of amplifier 74 is connected to DC-blocking capacitor 94 which is serially connected to a current-limiting potentiometer 95 to which the coupled resonant frequency is applied. The base of the amplifier 74 is also connected to the junction of a voltage

divider including resistances

97 and 98. As the transistor 74 conducts, the amplified signal is applied to the

tank circuit

80,81 in its collector which provides an alternating voltage of a frequency which is dependent upon the values of the capacitor 81 and the

capacitors

100 and 102 in the parallel resonant input circuits. The amplified signal is coupled through a detector circuit containing diode 104 serially connected to a parallel load including resistance 106 and capacitor 107 and applied as a negative signal to the base of transistor 73. A negative signal on the base of transistor 73 allows it to conduct, providing a current path through the coil SRR. Energization of the coil SRR opens its contacts SRR].

The relay contacts SRRl are in series circuit with a battery 110 (for example, 6 volts) and indicators such as an audible device 111 and a visible lamp 112. Thus, when the supervisory receiver is normally receiving, the coil SRR is energized, the contacts SRRI are open and the indicating devices 111 and 112 are deenergized. In the event of power failure at the supervisory transmitter or the supervisory receiver, the coil SRR becomes deenergized, closing the contacts SRRl and energizing the indicators 111 and 112. If it is desired to eliminate the noise of the audible indicator 111, such as a bell or buzzer, the circuit through the latter may be opened through a manually operable switch 114.

The battery 110 is preferably connected. to be trickle charged through a transformer 116 including a secondary in circuit with a

rectifier including diodes

117 and 118, and a resistance 120.

In order to prevent discharge of battery 110 during shipment, a pin switch 121 may be provided in circuit with alarms lll'and 112 to keep the circuit open until withdrawal of a manually accessible pin.

Referring now to the alarm receiver of FIG. 3, it will be noted that the receiver is similar in many respects to the supervisory receiver of FIG. 2 as a result of which a description of the entire circuitry will not be repeated. The similar components are designated by similar reference numbers with a prime suffix. The power supply to the circuit is similar in FIG. 3 to that in FIG. 2, the high frequency input signals are applied in similar manner, and the output of the receiver is similar in that when the circuit is receiving signals from the alarm transmitter channel in FIG. 1, a coil ARR is energized. In FIG. 3, energization of coil ARR is utilized to close its normally open contacts ARRl, whereas in FIG. 2, energization of the corresponding coil was utilized to open contacts. It should be understood that the circuit thus far described in FIG. 3, and the corresponding portion of FIG. 2, is substantially conventional, and may be obtained commercially.

The relay contacts ARRl in FIG. 3 are connected in circuit with a control relay coil CR connected across the transformer secondary, 72,77' so that when the contacts ARR] are closed, the coil CR is energized. Energization of the coil CR closes its normally open contact CR1 providing a holding circuit for the coil CR which is adapted to be broken when desired by means of a normally closed reset switch 122 adapted to be manually operated. Energization of the coil CR also closes normally open switch contacts CR2 in circuit with the transformer secondary leads 72,77' and in circuit with indicating devices including an audible indicator such as a bell or buzzer as at 124 and a visible lamp as at 125. Thus, when the receiver in FIG. 3 is receiving, the coil ARR is energized, closing the contacts ARRl, energizing the coil CR, closing the contacts CR2, and energizing the indicators '124 and 125, thereby to indicate the occurrence of fire or intrusion.

Referring now to the embodiment of FIGS. 4 and 5, the principles of the invention in the system of FIGS. l-3 is incorporated in a system for protecting a plurality of different areas in an industrial building or apartment building, for example, and indicating trouble at a single remote location such as a guard office or a caretakers office, while identifying the area of trouble. Toward the above ends, the circuit of FIG. 4 includes an alarm transmitter at 130 which may be similar to the alarm transmitter channel in FIG. 1 adapted to be supplied with power through leads 131 and 132 connected to the wiring in the building represented by

lines

133 and 134. The present system contemplates that there will be a plurality of alarm transmitters as at 130, one associated with each of the areas in an apartment building or industrial plant to be protected. Similarly, each of the protected areas will include one or more trouble indicating switches as at 136, corresponding to the switches 45 in FIG. 1, which may be fire or smoke detection devices or intrusion sensitive devices. The switches 136 are connected in circuit with an alarm transmitter relay coil 2ATR adapted to be energized on closure of one or more of the switch contacts 136. The coil ZATR is connected in series circuit with the switches 136 and a DC source of power represented by the secondary of a transformer 138 in association with a rectifier including diode 139 and capacitor 140. The primary of the transformer 138 is supplied from the installation wiring as by means of leads 142 and 143.

As in the system of FIGS. 1-3, the alarm relay coil 2ATR closes a pair of normally open contacts 2ATR1 to energize a local alarm indicator as at 145 connected across the leads 142 and 143 to provide a local indication at the source of the trouble that there is a problem which requires attention.

Additionally, energization of the coil 2ATR effects closure of its normally open contacts 2ATR2 which are adapted to control energization of the alarm transmitter 130 through the medium of a stepping relay 147.

A separate stepping relay 147 is provided at each of the areas or zones to be protected and the stepping relay performs the functions of indicating trouble and identifying the source of the trouble. More particularly, the stepping relay includes a plurality of stationary contacts as at 148, 149 and 150 adapted to be traversed by a rotary contact 151. The rotary contact is movable with a rachet 152 adapted to be indexed by a pawl 153 attractable by a relay pulse coil 155. The coil 155 is in circuit with the contacts 2ATR2 and with a source of power through

wires

156 and 158 which lead to the building wiring represented at 133 and 134. Associated with the relay 147 is a normally closed switch 160 in the wire 156 in circuit with the coil 155, so that when the pawl 153 is in the normal retracted position illustrated in FIG. 4, the switch is closed to permit energization of coil 155. In operation, when the pawl 153 is attracted by the coil 155, the switch 160 is opened, deenergizing the coil, so that the pawl is released to return to the retracted position where the switch 160 is again closed. In this manner, the stepping action of the relay is self-perpetuating, once the contacts 2ATR2 are closed, until such time as the stepping is self-interrupted as described below.

Interruption of the stepping action of the relay is provided through the medium of a pair of normally closed switch contacts 1R1 also in the wire 156 and adapted to be controlled by an interrupt relay coil IR. The coil IR is wired in circuit with one of the stationary switch contacts 149 and to the supply line 134 through' a lead 162. A circuit is adapted to be completed through the coil IR when the movable contact 151 reaches the stationary contact 150 in circuit with the coil. The center of the movable contact 151 is connected to the other supply line 133 through a lead 163. In operation, when the movable contact 151 causes energization of the coil IR, the contacts [R1 are opened and the stepping action of the relay is interrupted even though the switch 160 is closed. As will appear more clearly hereinbelow, the various stepping relays 147 in the different detection areas each have a different one of the

stationary contacts

148, 149, 150 wired in circuit with a coil as at IR, as a result of which each of the stepping relays is adapted to index a predetermined number of steps, one or more, and stop, but the number of steps in each relay is different. In this manner, similar relay constructions may be used in each of the areas merely by wiring the coil IR to a different stationary contact in each area, and the relays serve to identify the source of the signal indicating trouble.

In order to control the alarm transmitter 130 on actuation of the stepping relay 147, the alarm transmitter includes a pair of wires as at in circuit with a normally open switch 167 adapted to control energization of the transmitter on closure of the switch. That is, the switch 167 functions to energize the transmitter in the same manner that the switch 1ATR2 energizes the alarm transmitter channel in FIG. 1. The switch 167 is arranged for control by the stepping relay 147 so that each time the pawl 153 is attracted by the coil 155, the switch 167 is closed to energize the alarm transmitter. On each energization, the alarm transmitter sends a short signal. The number of signals sent by the alarm transmitter corresponds to the number of closures of the switch 167 which in turn corresponds with the number of steps the movable contact 151 is indexed, and of course the latter number differs in each area of detection.

Referring to FIG. 5, at an appropriate control station, there is a single alann receiver as at 170 which may correspond substantially with the alarm receiver illustrated in FIG. 3. The receiver 170 is connected by

wires

171 and 172 to the existing wiring as at 133 and 134 so that the latter supplies power for the receiver and also provides the medium by which carrier signals are transmitted from the alarm transmitter 130 to the alarm receiver 170. The output from the receiver 170 includes a pair of wires as at 174 and 175 connected in circuit with a switch in the receiver corresponding to the normally open switch ARRl in FIG. 3 so that when the receiver is receiving, the switch is closed, and a circuit may be made through the

wires

174 and 175, the former of which is connected to the existing wiring as at 134, and the latter of which leads to a relay pulse coil 177 in turn connected by wire 178 to the existing wiring 133. In this manner, each short signal burst at the receiver 170 results in a pulse applied to the coil 177.

The coil 177 attracts an indexing pawl 180 in a stepping relay 181 including a ratchet 182 indexed by the pawl 180 and rotatable with a movable switch contact 183 adapted to wipe across a plurality of stationary contacts as at 184, 185 and 186, for example. The center tap of the movable contact 183 is connected by a wire 188 to the existing wiring as at 133. The movable contact is adapted to complete a circuit through each of the stationary contacts, eachof which is wired through a different lamp as at 190, 191 and 192, for example, in turn connected with the existing wiring as at 134. Each of the lamps corresponds to a different detection area. For example, let it be assumedthat in connection with a detection area A, the first stationary contact 148 in the transmitter stepper relay would be wired to an interrupt coil IR. As a result, the detection of trouble in area A would result in indexing of movable contact 151 in the transmitter stepper a single step and indexing of the movable contact 183 in the receiver stepper relay a single step to thereby energize lamp 190, indicating trouble in area A. Similarly, if stationary contact 149 in FIG. 4 is wired to interrupt coil IR, the movable contact 183 in FIG. 5 will be indexed two steps to energize lamp B. In area C, if stationary contact 150 is wired to coil IR, movable contact 183 will index three steps and stop at stationary contact 186 to energize lamp 192 indicating trouble in area C.

As the system is operated, with the pawl 153 in FIG. 4 indexing the ratchet 152, the latter is spring biased toward the home or starting position and is retained at each indexed position by means such as a retention pawl 194. After operation of the system, when it is desired to put it back into use, the stepper relay may be reset by means of a reset coil 196 adapted to attract the retention pawl 194, allowing return of the rachet 152 to the home position. The coil 196 may be wired across the

lines

133 and 134 through a normally open pushbutton reset switch 198.

In similar manner, the rachet 182 in FIG. 5 may be biased toward the home or starting position and held in indexed positions by means of retention pawl 200 adapted to be withdrawn for reset by energization of a coil 202 energizable through a normally open reset switch 204.

Supervision of the system thus far described in FIGS. 4 and 5 is preferably provided by a single supervisory transmitter as at 210 which may be similar to the supervisory transmitter channel 11 in FIG. 1 and connected to the

house wiring

133, 134 as by

wires

211 and 212 which provide a power supply to the transmitter and provide the vehicle by which the supervisory transmitter signals are applied to the

wiring

133, 134. In order to provide appropriate supervision, the transmitter 210 is associated with the alarm transmitter 130 located at the most remote detection area so as to be capable of determining the loss of power or a line break at any place between the source of power and the end of the extension system most remote from the source of power. Energization of the transmitter 210 is controlled by normally open relay switch contacts 2STR2 in circuit with the transmitter through leads 215 and 216. The switch 2STR2 corresponds with that shown at 1STR2 in the supervisory transmitter channel in FIG. 1. The normally open contacts 2STR2 are adapted to be controlled by a supervisory transmitter relay winding 2STR in circuit with the alarm relay winding 2ATR at the most remote detection area.

As in the system of FIG. 1, the circuit including the windings 2ATR and 2STR also has a relatively high resistance as at 218 in parallel with the detection switches 136 so that when the latter are open, there is normally a low-current high-resistance circuit adapted to energize the supervisory winding 2STR while leaving the alarm winding 2ATR deenergized. Energization of the winding 2STR closes the contacts 2STR2 so that the supervisory transmitter 210 is normally transmitting as in FIG. 1. At the same time, energization of the coil 2STR opens the normally closed contacts 2STR] preventing energization of trouble indicators such as visible lamp 220 and audible bell 221, in circuit with the contacts 2STR1 and a battery 222. So long as the power supply is operative, the battery is trickle charged by means of a rectifier 225 which may be connected with leads 142 and 143.

In event of power failure in the most remote detection area or at any detection area between the most remote and the source of power supply to the house, the winding 2STR is deenergized, closing contacts 2STR1, energizing the

indicators

220 and 221. The noise of the latter may be discontinued if desired by opening a manual switch 227.

In operation, the supervisory transmitter 210 supplies signals at a frequency adapted to be received by a supervisory receiver as at 230 (FIG. 5) corresponding substantially to that illustrated in FIG. 2 and adapted to be connected to the house wiring by

leads

231 and 232 which provide power supply and transmit carrier signals to the receiver. The receiver includes internally a switch corresponding to that at SRRl in FIG. 2 adapted to be held open as long as the receiver is receiving. On failure to receive, the switch closes to complete a circuit from a battery 233 to audible indicator 234 and visible indicator 235, the former of which may be silenced by opening manual switch 236. The battery is trickle charged through a rectifier 237 connected across the house wiring.

It will be understood that in all the detection areas but the most remote the supervisory transmitter will be omitted and the controls associated with it will be unnecessary.

In order to restore the system of FIG. 4 to normal after energization of alarm relay 2ATR, a manual reset switch 238 is provided in circuit with the coils 2ATR and 2STR to be opened to deenergize both coils for putting the system into service again.

Iclaim:

1. A detection and alarm system utilizing high frequency signals transmitted over existing wiring in a building or the like, comprising,

a. a fire-detecting transmitter circuit located for sensing a dangerous fire condition and transmitting signals,

b. a fire alarm receiver circuit located remotely from the fire-detecting transmitter circuit for receiving signals transmitted by the fire detecting transmitter circuit and indicating a fire condition,

0. a supervisory transmitter circuit associated with the firedetecting transmitter circuit and normally energized to transmit signals when the fire-detecting circuit is in operative condition, and a warning receiver circuit located adjacent the fire alarm receiver circuit for normally receiving signals from the supervisory transmitter circuit and indicating a warning on failure to receive.

2. A detection and alarm system as defined in claim 1, wherein the firedetecting transmitter includes fire detection means for sensing a dangerous fire condition, and transmitter energizable responsive to the detection means in event of said condition for transmitting signals.

3. A detection and alarm system as defined in claim 1, wherein the fire alarm receiver circuit includes a receiver for receiving signals when transmitted by the fire-detecting transmitter, and an indicator energizable responsive to the alarm receiver when receiving.

4. A detection and alarm system as defined in claim 1, wherein the supervisory transmitter circuit includes a transmitter for sending signals when energized, and a power supply common to the fire-detecting transmitter circuit and the supervisory transmitter circuit for normally maintaining the supervisory transmitter energized in the absence of power failure.

5. A detection and alarm system as defined in claim 1, wherein the warning receiver circuit includes a receiver for receiving signals when transmitted by the supervisory transmitter, and an indicator energizable responsive to the warning receiver on failure to receive.

6. A fire detection and alarm system for utilizing high frequency signals transmitted over existing wiring in a building or the like, comprising,

a. a fire-detecting transmitter adapted to be connected to the existing wiring for power supply including means for sensing a dangerousfire condition and means responsive to the sensing means for transmitting signals of a first predetermined frequency over the existing wiring indicative of the fire condition, a fire alarm receiver adapted to be connected to the existing wiring for power supply and located remotely from the fire-detecting transmitter including means for receiving signals of said first frequency from the existing wiring transmitted by the fire-detecting transmitter and means responsive to the receiving means for issuing an alarm indicating a fire condition, c. a supervisory transmitter associated with the fire-detecting transmitter and adapted to be connected with the existing wiring for power supply including means normally energized thereby to transmit signals of a second predetermined frequency over the existing wiring when the power supply to the fire-detecting transmitter is operative, and a warning receiver associated with the fire alarm receiver and adapted to be connected to the existing wiring for power supply including means for normally receiving signals of said second frequency from the existing wiring transmitted by the supervisory transmitter and means responsive to the receiving means for issuing a warning indicating trouble on failure to receive. 7. A combination as defined in claim 6, said sensing means including a normally open sensing switch in circuit with a normally deenergized high current relay controlling said transmitting means of the first frequency, said supervisory transmitter including a normally energized low-current relay controlling said transmitting means of the second frequency and in circuit with a source of power and the high-current relay, and a relatively high resistance in parallel with the normally open sensing switch, so that the supervisory low-current relay is normally energized in the absence of failure of the power source and is deenergized on failure of the power source, and the detecting low-current relay is normally deenergized and becomes energized on closure of the sensing switch. 8. A detection and alarm system as defined in claim 6, said fire-detecting transmitter including an oscillatorin circuit with a normally open switch, a normally deenergized high-current relay coil controlling said normally open switch, and a normally open fire-detecting switch in circuit with the normally deenergized relay coil and adapted to be closed in response to a dangerous fire condition to energize the relay coil, thereby to close the relay switch and energize the oscillator to transmit signals to the fire alarm receiver. 9. A combination as defined in claim 8, said supervisory transmitter comprising an oscillator in circuit with relay switch contacts, and a normally energized low-current relay coil holding the switch contacts closed in the absence of power failure. 10. A combination as defined in claim 9, said fire detection transmitter and said supervisory trans mitter including a common control circuit having said relay coils in series circuit and in series with at least one normally open fire detection switch, and a relatively high resistance in parallel with the fire detection switch and completing a circuit to maintain the supervisory relay normally energized in the absence of power failure, the arrangement being such that on closure of the fire detection switch the resistance is shunted and the detecting relay is energized. 11. A combination as defined in claim 6, wherein the waming means in the warning receiver includes a battery normally connected with the existing wiring for charging, an indicator and a normally nonconductive switching device in circuit with the battery and means controlled by the warning receiver for rendering the switching device conductive on failure to receive, said alarm means in the alarm receiver comprising an indicator and a normally nonconductive switching device in circuit with the existing wiring, and means controlled by the fire alarm receiver for rendering the switching device conductive on receiving. 1

12. A combination as defined in claim 6, including a local alarm associated with the fire alarm detecting transmitter including an indicator and a normally nonconductive switching device in circuit with the existing wiring together with means controlled by the transmitter for rendering the switching device conductive during transmission, and a local alarm associated with the supervisory transmitter including a battery in circuit with the existing wiring to normally be charged thereby, an indicator and a normally nonconductive switching device in circuit with the battery together with means responsive to the supervisory transmitter for rendering the switching device conductive on failure to transmit.

13, In an alarm system for protecting a plurality of different areas in a building or the like and indicating trouble at a single remote location and identifying the area of trouble,

a. a rotary switch associated with each area including means for advancing a movable contact one or more increments to a stationary contact located at a different increment for each area,

b. a trouble-indicating switch in each area in circuit with the advancing means and with a source of power and operable for energizing the advancing means in event of trouble,

c. an interruptor associated with each advancing means operable to stop the movable contact at the stationary contact located at a different increment for each area,

. a transmitter associated with each rotary switch and energized once for each increment of movement of the associated movable contact for transmitting a signal,

e. a receiver energizable responsive to signals from any of the transmitters,

f. an annunciator at an indicating station having means responsive to receiver energization for advancing a movable contact relative to a plurality of stationary contacts a distance of one stationary contact for each receiver energization, and

g. a plurality of indicating devices in circuit respectively with the stationary annunciator contacts each for indicating trouble in a different area and identifying the area.

14. In an alarm system for protecting a plurality of different areas in a building or the like and indicating trouble at a single remote location and identifying the area of trouble,

a. a plurality of stepping switches one associated with each area, each including means for advancing a movable contact relative to a plurality of stationary contacts,

a trouble-indicating switch in each area in circuit with the advancing means and with a source of power and operable for energizing the advancing means in event of trouble,

c. an interrupt switch in circuit with each advancing means and operable to deenergize the same,

. an interruptor for each area operable at a different position of the movable contact for each area to actuate the interrupt switch,

e. a signal switch associated with each stepping switch actuated repeatedly once for each stationary contact transversed by the movable contact,

f. a transmitter in circuit with each signal switch to be momentarily energized -.on each switch actuation for transmitting a signal,

g. a receiver energizable responsive to signals from any of the transmitters,

h. an annunciator at an indicating station having means responsive to receiver energization for advancing a movable contact relative to a plurality of stationary contacts a distance of one stationary contact for each receiver energized, and

i. a plurality of indicating devices in circuit respectively with the stationary annunciator contacts each for indicating trouble in a different area and identifying the area.

15. In an alarm system for protecting a plurality of different areas in a building or the like and indicating trouble at a single remote location and identifying the area of trouble,

a. a plurality of stepping relays one associated with each area, each including a coil for stepping a movable contact relative to a plurality of stationary contacts,

b. a trouble-indicating switch in each area. in contact with the stepping coil and with a source of power and operable for energizing the stepping coil in event of trouble,

c. an interrupt switch in circuit with each stepping coil operable to deenergize the same,

(1. an interrupt coil for each'area in circuit with a different stationary contact for each area energizable to actuate the interrupt switch at a different position in each area,

e. a signal switch with each stepping relay actuated once for each stationary contact traversed by the movable contact,

f. a transmitter in circuit with each signal switch and energized momentarily on each switch actuation for transmitting a signal,

g. a receiver energizable momentarily responsive to each signal from any of the transmitters,

h. a control switch operated momentarily responsive to each receiver energization,

i. an annunciator relay at an indicating station having a stepping coil controlled by said receiver switch for advancing a movable contact relative to a plurality of stationary contacts a distance of one stationary contact for each control switch actuation, and

j. a plurality of indicating lamps in circuit respectively with the last-recited stationary contacts each for indicating trouble in a different area and identifying the trouble area.

16. A combination as defined in claim 15, each stepping relay including a pawl and ratchet device having a pawl attractable by said stepping coil and a ratchet actuated by the pawl for advancing the movable switch contact responsive to operation of the trouble-indicating switch, a stepper switch in circuit with the stepper coil and operated by the pawl on each actuation of the latter thereby to deenergize the coil, and

means for returning the pawl to close the stepper switch thereby to reenergize the stepper coil for the next step.

17. A combination as defined in claim-l wherein said annunciator relay includes a pawl and ratchet device having a pawl attractable by said stepper coil and a ratchet actuated by the pawl for driving the movable contact, and means for returning the pawl on deenergization of the stepper coil.

18. In an alarm system for protecting a plurality of different areas in a building or the like and indicating trouble at a single remote location and identifying the area of trouble, utilizing high frequency carrier signals transmitted over existing wiring, a. a rotary switch associated with each area including means for advancing a movable contact one or more increments to a stationary contact located at a different increment for each area,

d. an alarm transmitter associated with each rotary switch and energized once for each increment of movement of the associated movable contact for transmitting a signal,

e. an alarm receiver energizable responsive to signals from any one of the alarm transmitters,

f. an annunciator at an indicating station having means responsive to alarm receiver energization for advancing a movable contact relative to a plurality of stationary contacts a distance of one stationary contact for each alarm receiver energization,

g. a plurality of indicating devices in circuit respectively with the stationary annunciator contacts each for indicating trouble in a difierent area and identifying the area,

h. means connecting each alarm transmitter to the existing building wiring for power supply,

i. means connecting the alarm receiver to the existing wiring for power supply,

j. a supervisory transmitter connected to the existing wiring for power supply adjacent the most remote alarm transmitter and normally energized to transmit signals when the power supply is operative, and

k. a supervisory receiver connected to the existing wiring for power supply adjacent the alarm receiver for normally receiving signals from the supervisory transmitter and indicating a warning on failure of power supply to the supervisory transmitter or supervisory receiver.

19. A combination as defined in claim 18 including a normally open sensing switch in each area in circuit with a normally deenergized high current relay controlling the associated trouble-indicating switch.

20. A combination as defined in claim 19 including a normally energized low-current relay controlling the supervisory transmitter and in circuit with the high current relay in the most remote area and the existing wiring for power supply, a relatively high resistance in parallel with the nonnally open sensing switch in the most remote area so that the supervisory low current relay is normally energized in the absence of failure of the power source and is deenergized on failure of the power source, and the detecting low-current relay is normally deenergized and becomes energized on closure of the sensing switch.

21. In an alarm system for protecting a plurality of different areas in a building or the like and indicating trouble at a single remote location and identifying the area of trouble,

a. a transmitter associated with each area for sending signals therefrom,

b. means for energizing each transmitter momentarily a different number of times to indicate trouble and the source thereof by the number of signals sent,

c. a receiver energizable responsive to signals from any of the transmitters,

d. an annunciator at an indicating station having means responsive to receiver energization for advancing a movable contact relative to a plurality of stationary contacts a distance of one stationary contact for each receiver energization, and

e. a plurality of indicating devices in circuit respectively with the stationary annunciator contacts each for indicating trouble in a different area and identifying the area.

22. In an alarm system for protecting a plurality of different areas in a building or the like and indicating trouble at a single remote location and identifying-the area of trouble,

a. a rotary switch associated with each area including means for advancing a movable contact one or more increments to a stationary. contact located at a different increment for each area,

d. a transmitter associated with each rotary switch and energized once for each increment of movement of the associated movable contact for transmitting a signal,

e. a receiver energizable responsive to signals from any of the transmitters,

ferent number of times to indicate trouble and the source thereof by the number of signals sent,

c. a receiver energizable responsive to signals from any of the transmitters,

d. a plurality of indicating devices each for indicating trouble in a different area and identifying the area, and

e. means responsive to the receiver for selectively energizing the indicating devices depending on the number of signals received.

Claims

1. A detection and alarm system utilizing high frequency signals transmitted over existing wiring in a building or the like, comprising, a. a fire-detecting transmitter circuit located for sensing a dangerous fire condition and transmitting signals, b. a fire alarm receiver circuit located remotely from the firedetecting transmitter circuit for receiving signals transmitted by the fire detecting transmitter circuit and indicating a fire condition, c. a supervisory transmitter circuit associated with the firedetecting transmitter circuit and normally energized to transmit signals when the fire-detecting circuit is in operative condition, and d. a warning receiver circuit located adjacent the fire alarm receiver circuit for normally receiving signals from the supervisory transmitter circuit and indicating a warning on failure to receive.

2. A detection and alarm system as defined in claim 1, wherein the fire-detecting transmitter includes fire detection means for sensing a dangerous fire condition, and a transmitter energizable responsive to the detection means in event of said condition for transmitting signals.

6. A fire detection and alarm system for utilizing high frequency signals transmitted over existing wiring in a building or the like, comprising, a. a fire-detecting transmitter adapted to be connected to the existing wiring for power supply including means for sensing a dangerous fire condition and means responsive to the sensing means for transmitting signals of a first predetermined frequency over the existing wiring indicative of the fire condition, b. a fire alarm receiver adapted to be connected to the existing wiring for power supply and located remotely from the fire-detecting transmitter including means for receiving signals of said first frequency from the existing wiring transmitted by the fire-detecting transmitter and means responsive to the receiving means for issuing an alarm indicating a fire condition, c. a supervisory transmitter associated with the fire-detecting transmitter and adapted to be connected with the existing wiring for power supply including means normally energized thereby to transmit signals of a second predetermined frequency over the existing wiring when the power supply to the fire-detecting transmitter is operative, and d. a warning receiver associated with the fire alarm receiver and adapted to be connected to the existing wiring for power supply including means for normally receiving signals of said second frequency from the existing wiring transmitted by the supervisory transmitter and means responsive to the receiving means for issuing a warning indicating trouble on failure to receive.

7. A combination as defined in claim 6, said sensing means including a normally open sensing switch in circuit with a normally deenergized high current relay controlling said transmitting means of the first frequency, said supervisory transmitter including a normally energized low-current relay controlling said transmitting means of the second frequency and in circuit with a source of power and the high-current relay, and a relatively high resistance in parallel with the normally open sensing switch, so that the supervisory low-current relay is normally energized in the absence of failure of the power source and is deenergized on failure of the power source, and the detecting low-current relay is normally deenergized and becomes energized on closure of the sensing switch.

8. A detection and alarm system as defined in claim 6, said fire-detecting transmitter including an oscillator in circuit with a normally open switch, a normally deenergized high-current relay coil controlling said normally open switch, and a normally open fire-detecting switch in circuit with the normally deenergized relay coil and adapted to be closed in response to a dangerous fire condition to energize the relay coil, thereby to close the relay switch and energize the oscillator to transmit signals to the fire alarm receiver.

9. A combination as defined in claim 8, said supervisory transmitter comprising an oscillator in circuit with relay switch contacts, and a normally energized low-current relay coil holding the switch contacts closed in the absence of power failure.

10. A combination as defined in claim 9, said fire detection transmitter and said supervisory transmitter including a common control circuit having said relay coils in series circuit and in series with at least one normally open fire detection switch, and a relatively high resistance in parallel with the fire detection switch and completing a circuit to maintain the supervisory relay normally energized in the absence of power failure, the arrangement being such that on closure of the fire detection switch the resistance is shunted and the detecting relay is energized.

11. A combination as defined in claim 6, wherein the warning means in the warning receiver includes a battery normally connected with the existing wiring for charGing, an indicator and a normally nonconductive switching device in circuit with the battery and means controlled by the warning receiver for rendering the switching device conductive on failure to receive, said alarm means in the alarm receiver comprising an indicator and a normally nonconductive switching device in circuit with the existing wiring, and means controlled by the fire alarm receiver for rendering the switching device conductive on receiving.

13. In an alarm system for protecting a plurality of different areas in a building or the like and indicating trouble at a single remote location and identifying the area of trouble, a. a rotary switch associated with each area including means for advancing a movable contact one or more increments to a stationary contact located at a different increment for each area, b. a trouble-indicating switch in each area in circuit with the advancing means and with a source of power and operable for energizing the advancing means in event of trouble, c. an interruptor associated with each advancing means operable to stop the movable contact at the stationary contact located at a different increment for each area, d. a transmitter associated with each rotary switch and energized once for each increment of movement of the associated movable contact for transmitting a signal, e. a receiver energizable responsive to signals from any of the transmitters, f. an annunciator at an indicating station having means responsive to receiver energization for advancing a movable contact relative to a plurality of stationary contacts a distance of one stationary contact for each receiver energization, and g. a plurality of indicating devices in circuit respectively with the stationary annunciator contacts each for indicating trouble in a different area and identifying the area.

14. In an alarm system for protecting a plurality of different areas in a building or the like and indicating trouble at a single remote location and identifying the area of trouble, a. a plurality of stepping switches one associated with each area, each including means for advancing a movable contact relative to a plurality of stationary contacts, b. a trouble-indicating switch in each area in circuit with the advancing means and with a source of power and operable for energizing the advancing means in event of trouble, c. an interrupt switch in circuit with each advancing means and operable to deenergize the same, d. an interruptor for each area operable at a different position of the movable contact for each area to actuate the interrupt switch, e. a signal switch associated with each stepping switch actuated repeatedly once for each stationary contact traversed by the movable contact, f. a transmitter in circuit with each signal switch to be momentarily energized on each switch actuation for transmitting a signal, g. a receiver energizable responsive to signals from any of the transmitters, h. an annunciator at an indicating station having means responsive to receiver energization for advancing a movable contact relative to a plurality of stationary contacts a distance of one stationary contact for each receiver energized, and i. a plurality of indicating devices in circuit respecTively with the stationary annunciator contacts each for indicating trouble in a different area and identifying the area.

15. In an alarm system for protecting a plurality of different areas in a building or the like and indicating trouble at a single remote location and identifying the area of trouble, a. a plurality of stepping relays one associated with each area, each including a coil for stepping a movable contact relative to a plurality of stationary contacts, b. a trouble-indicating switch in each area in contact with the stepping coil and with a source of power and operable for energizing the stepping coil in event of trouble, c. an interrupt switch in circuit with each stepping coil operable to deenergize the same, d. an interrupt coil for each area in circuit with a different stationary contact for each area energizable to actuate the interrupt switch at a different position in each area, e. a signal switch with each stepping relay actuated once for each stationary contact traversed by the movable contact, f. a transmitter in circuit with each signal switch and energized momentarily on each switch actuation for transmitting a signal, g. a receiver energizable momentarily responsive to each signal from any of the transmitters, h. a control switch operated momentarily responsive to each receiver energization, i. an annunciator relay at an indicating station having a stepping coil controlled by said receiver switch for advancing a movable contact relative to a plurality of stationary contacts a distance of one stationary contact for each control switch actuation, and j. a plurality of indicating lamps in circuit respectively with the last-recited stationary contacts each for indicating trouble in a different area and identifying the trouble area.

16. A combination as defined in claim 15, each stepping relay including a pawl and ratchet device having a pawl attractable by said stepping coil and a ratchet actuated by the pawl for advancing the movable switch contact responsive to operation of the trouble-indicating switch, a stepper switch in circuit with the stepper coil and operated by the pawl on each actuation of the latter thereby to deenergize the coil, and means for returning the pawl to close the stepper switch thereby to reenergize the stepper coil for the next step.

17. A combination as defined in claim 15 wherein said annunciator relay includes a pawl and ratchet device having a pawl attractable by said stepper coil and a ratchet actuated by the pawl for driving the movable contact, and means for returning the pawl on deenergization of the stepper coil.

18. In an alarm system for protecting a plurality of different areas in a building or the like and indicating trouble at a single remote location and identifying the area of trouble, utilizing high frequency carrier signals transmitted over existing wiring, a. a rotary switch associated with each area including means for advancing a movable contact one or more increments to a stationary contact located at a different increment for each area, b. a trouble-indicating switch in each area in circuit with the advancing means and with a source of power and operable for energizing the advancing means in event of trouble, c. an interruptor associated with each advancing means operable to stop the movable contact at the stationary contact located at a different increment for each area, d. an alarm transmitter associated with each rotary switch and energized once for each increment of movement of the associated movable contact for transmitting a signal, e. an alarm receiver energizable responsive to signals from any one of the alarm transmitters, f. an annunciator at an indicating station having means responsive to alarm receiver energization for advancing a movable contact relative to a plurality of stationary contacts a distance of one stationary contact for each alarm receiver energization, g. a plurAlity of indicating devices in circuit respectively with the stationary annunciator contacts each for indicating trouble in a different area and identifying the area, h. means connecting each alarm transmitter to the existing building wiring for power supply, i. means connecting the alarm receiver to the existing wiring for power supply, j. a supervisory transmitter connected to the existing wiring for power supply adjacent the most remote alarm transmitter and normally energized to transmit signals when the power supply is operative, and k. a supervisory receiver connected to the existing wiring for power supply adjacent the alarm receiver for normally receiving signals from the supervisory transmitter and indicating a warning on failure of power supply to the supervisory transmitter or supervisory receiver.

20. A combination as defined in claim 19 including a normally energized low-current relay controlling the supervisory transmitter and in circuit with the high current relay in the most remote area and the existing wiring for power supply, a relatively high resistance in parallel with the normally open sensing switch in the most remote area so that the supervisory low current relay is normally energized in the absence of failure of the power source and is deenergized on failure of the power source, and the detecting low-current relay is normally deenergized and becomes energized on closure of the sensing switch.

21. In an alarm system for protecting a plurality of different areas in a building or the like and indicating trouble at a single remote location and identifying the area of trouble, a. a transmitter associated with each area for sending signals therefrom, b. means for energizing each transmitter momentarily a different number of times to indicate trouble and the source thereof by the number of signals sent, c. a receiver energizable responsive to signals from any of the transmitters, d. an annunciator at an indicating station having means responsive to receiver energization for advancing a movable contact relative to a plurality of stationary contacts a distance of one stationary contact for each receiver energization, and e. a plurality of indicating devices in circuit respectively with the stationary annunciator contacts each for indicating trouble in a different area and identifying the area.

22. In an alarm system for protecting a plurality of different areas in a building or the like and indicating trouble at a single remote location and identifying the area of trouble, a. a rotary switch associated with each area including means for advancing a movable contact one or more increments to a stationary contact located at a different increment for each area, b. a trouble-indicating switch in each area in circuit with the advancing means and with a source of power and operable for energizing the advancing means in event of trouble, c. an interruptor associated with each advancing means operable to stop the movable contact at the stationary contact located at a different increment for each area, d. a transmitter associated with each rotary switch and energized once for each increment of movement of the associated movable contact for transmitting a signal, e. a receiver energizable responsive to signals from any of the transmitters, f. a plurality of indicating devices each for indicating trouble in a different area and identifying the area, and g. means responsive to the receiver for selectively energizing the indicating devices depending on the number of signals received.

23. In an alarm system for protecting a plurality of different areas in a building or the like and indicating trouble at a single remote location and identifying the areA of trouble, a. a transmitter associated with each area for sending signals therefrom, b. means for energizing each transmitter momentarily a different number of times to indicate trouble and the source thereof by the number of signals sent, c. a receiver energizable responsive to signals from any of the transmitters, d. a plurality of indicating devices each for indicating trouble in a different area and identifying the area, and e. means responsive to the receiver for selectively energizing the indicating devices depending on the number of signals received.