US2779936A

US2779936A - Supervisory unit for burglar alarm system

Info

Publication number: US2779936A
Application number: US495486A
Authority: US
Inventors: Loudon Clifford Lee; William E Riker
Original assignee: HOLMES ELECTRIC PROTECTIVE CO
Current assignee: HOLMES ELECTRIC PROTECTIVE CO
Priority date: 1955-03-21
Filing date: 1955-03-21
Publication date: 1957-01-29
Anticipated expiration: 1974-01-29

Description

1957 c. I LOUDON ET AL. I 2,779,936

SUPERVISORY UNIT FOR BURGLAR ALARM SYSTEM Filed March 21, 1955 2 Sheets-Sheet 1 7 8o POWERSUPPLY I I304 I00 I I. T 58a 4 58b k; I06 5+ T Ii TO OSCILLATOR PLATE 60 IN TRANSMITTER L\ r I 13 55 6| l4 TRANSMITTER MAIN POWER I N UNIT SUPPLY UNIT I Io l 3 i 6 l6 30 34 ,32 FL 7 1 j INVENTORS RECEIVER 22 28 gt UNIT I I SUPERV|SQRY [a 1 UN I T ;-C'lz ]"0rd LLovdon BY Hm/0.2%

ATTORN E Y SUPERVISORY UNIT FOR BURGLAR ALARM SYSTEM Application March 21, 1955, Serial No. 495,486

14 Claims. or. 340-258) The present invention relates to a supervisory unit for use with a burglar alarm system, and in particular, to a supervisory unit for use with a burglar alarm system which detects the presence of an intruder in the protected area as a result of the disturbance of a complex pattern of ultrasonic sound waves. Most burglar alarm systems operate on the change of or interruption in a normal energy flow caused by the presence or entrance of an intruder. Therefore, it is comparatively simple to supervise the effectiveness of such a system since it is merely necessary to determine whether or not there is a normal flow of energy in the system. However, the system with which the present invention is to be used is a space type which operates upon the conversion of energy rather than the interruption of energy flow. In this system ultrasonic waves at a fixed frequency are propagated in the enclosure to be protected thereby establishing a standing wave pattern. A microphone also located in the enclosure picks up these waves and converts the sound energy to electrical energy. Ifthese waves are disturbed the amount of energyand the frequency of the waves change and the alarm will be actu- I ated.

It can be seen from this that this type of system is far more diflicult to supervise than the system initially described above sinceiit is diflicultto test the energy. conversion characteristics of the system without producing an erroneous alarm.

It is'an object of the present invention to provide a supervisory unit for a space type burglar alarm system which provides a periodic check of the operation of the system.

It is another object of the present invention to provide a. supervisory unit which periodically tests the operability of its associated burglar alarm system.

It is another object of the present invention to provide a supervisory unit for a burglar alarm system 'which is periodically tested automatically and which may be tested, when desired, from a remote point.

It is another'object of the present invention to provide a supervisory unit for a space type burglar alarm system.

It is another object of the present invention to provide a supervisory unit for periodically checking the operability of a space type burglar alarm system which also provides circuits for detecting malfunctioning of the supervisory unit.

It is a further object of the present invention to provide a supervisory unit for checking the operability of. a space type burglar alarm system by simulating the presence of an intruder in the protected enclosure.

It is still another object of the'present invention to provide a supervisoryunit for automatically checking the operability of a space type burglar alarm system which upon detecting a failure in the system sendsan indication to the central office which is difierent'fromrthe indication :supplied when an intruder is detected in the enclosure.

nited States Patent provide a supervisory unit for automatically checking the operability of a space type burglar alarm system which provides for automatic periodic testing that is initiated at the protected enclosure and also provides for the initiationof tests from a remote'point, the two testcircuits being independent of one another.

In the drawings: a 1

Fig. 1 is a block diagram showing the system in which the present invention is to be used;

Fig. 2 is a circuit diagram of the supervisory unit of the present invention; I

Fig. 3 is a circuit diagram of the supervisory unit showing the position of the relays during the period of a local test.

Referring to Fig. L'ultrasonic waves at a frequency of approximately 17 kc./s. are propagated, in the enclosure to be protected, by means of a loudspeaker 10. The transmitter unit 12 which supplies electrical energy of the proper frequency to the loudspeaker 10 receives its power from a power supply 16 over the line 14. The ultrasonic waves which are emitted by the speaker 10 undergo a complex process of reflection and absorption which sets up a standing wave pattern within the enclosure. These standing waves are picked up by the microphone 18 and converted to electrical energy which is fed to the receiver unit 20. If there is no disturbance in the room the receiver unit 20 will have supplied to it an unmodulated 17 kc. wave. The receiver which is the subject of copending application Ser. No. 495,484, filed by Loudon and Riker, on March 21, 1955, detects any modulation of the 17 kc. wave. If the wave is unmodulated there will be no output from the receiver unit. If, however, an intruder enters the enclosure his movements will both amplitude modulate and frequency modulate the 17 kc. carrier. Both portions of this wave will be detected by the receiver unit thereby producing an A.-C. output which will be fed over the

lines

22 and 24 to the supervisory unit 26. Upon receipt of such a signal the supervisory unit will sound an alarm in the central otfice; connection between the supervisory unit and the central ofiice being over

lines

28 and 40. The receiver unit 20 and supervisory unit 26 receive power from the main power supply unit 16 over lines 32 and'34 and 36 and 38 respectively. Another output of the supervisory unit 26 is connected to the transmitter unit 12 over the line 30 for reasons to be explained further on in the specification. 'The operation of the supervisory unit' will'now be explained with reference being made to Figs. 2 and 3. As previously explained, the supervisory unit is connected to the central office by means of the

lines

28 and 40. The central oifice circuit is essentially thesame as shown in the Miranda Patent No. 1,881,832, issued October 11, 1932. These lines are connected to a voltage supply 41 at the central ofiice which normally maintains a direct current, of say 12 milliamperes, in :a circuit in the supervisory unit which consists of the signaling device 42, line 44, changer magnet 46, the front coil 48b of the differential relay 48, line 50, line 52, the forward contact 54a of the relay 54, the armature 54b, line 56, the front contact 58a and armature 58b of the relay 58, line 60, the other coil 48a, shunt 48s of the differential relay 48, the line 62, the resistor 64, the line 66, resistor 68, line 70 and line 28. The 12 milliamperes flowing through this circuit are insuflicient to cause actuation of .allel with the armature 78a and contact 78c.

the relay such that the armature 48d is not engaging the contact 48c.

The above conditions as already indicated prevail under normal operation. If an intruder enters the building or for some other reason a signal occurs in the output of the receiver unit 20, a signal is developed-in the transformer winding 72. The signal is rectified by the rectifier 74 and filtered by the condenser 76. The resulting direct current is applied to the relay 78 thereby actuating the relay. Upon actuation the relay pulls the

armatures

78a and 78b into engagement with the contacts 780 and 78d respectively. Upon the engagement of the armature 78a with contact 78c, a portion. of the circuit in which the 12 milliamperes are normally flowing'is shorted. The current from the central office now flows from line '49 through the signaling device 42, line 44, change'r'magnet relay 4.6, the coil 4% of the differential relay 48, line 50, line 80,

' contact82b of the switch 82 which is normally closed,

1ine84', armature 78a, contact 78c, line 86, line 85 and back to the central office over' line 28. Therefore, the

,coil 48a of the differential relay'48, resistor 64 and resistor 68 have been shunted.

The elimination of these elements from the circuit causes an increase in current to, say 17 milliamperes. At the central office the pointer 43 is caused to move by the increased current and touches one of the contacts 47. This energizes the relay 49 which drops the armature 51 onto the contact 53 which energizes the alarm 55 thereby indicating at the central office the presence of the intruder. Since the current flow through the coil 48a of the differential relay 48 has been interrupted, the armature 48d is caused to engage the contact 48c. This circuit is in par- The increased current will now be maintained even though signals may no longer be received from the receiver unit 20. The system may be reset by someone investigating the alarm or by opening the entire central oflice circuit at the central office.

In providing supervisory control of the overall system, it has been found convenient to test the operation of the relay 78 as an indication .of proper functioning 'of the system. These tests are made automatically at 30-second intervals and also may be made at any time from the central office. During these tests the normal signal emitted by the transmitter and loudspeaker is altered to simulate the signal that would be produced by an intruder moving through the room. At the same time that the normal signal isdisrupted, the contacts of relay 78 are disconnected from the central office :circuit. The modulated signal is picked up by the microphone 18 and amplified, detected and rectified by the receiver unit 20.

This signal is applied to the relay 78 again causing it to attract the

armatures

78a and 78b. Upon closure of the armature 78b and contact 78d the condenser 87 in I .the grid circuit of the tube 88 begins to receive a charge from a power supply connected to the line 90 The conduction of the tube 88 maintains the

armatures

92a and 54b of the

relays

92 and 54 respectively in the positions shown in the Figure 3. It will be noted that the armature 54b and contact 54a of the relay 54 are in the central office circuit previously described; The relay 54 is chosen so that it will remain actuated by a current which is somewhat less than'full plate current of the tube 33. Therefore, as the voltage on the grid of the tube 38 decreases as a result of the discharge of the condenser 87 through the resistor M5 in the interval between test periods, the current in the platecircuit will not decrease sufilciently to cause de-energization of the relay 54 unless the 5 condenser 87 is allowed to discharge, without recharging, for several test intervals. If the chargeon the condenser does fall sufficiently due to malfunctioning of the relay 78 for several test periods, the current through the relay 54b to assume the non-operative position. This willopen the

contacts

54a and 54b inthe central'office circuit'and :54 will be decreased sufiicientlyto allow the armature f r r b 4 therefore interrupt the 12 milliamperes current indicating that the system is malfunctioning.

The automatic tests are controlled by the operation of the motor 96. The motor drives the two cam Wheels 82 and as through the gear train 99 at a rate determined by the number of test operations desired per minute. As pointed out above, the present system operates-attwo tests per minute and therefore the cams are driven at one revolution per minute. Each cam has two notches in its circumference spaced approximately 180 degrees apart. Cam followers 82a and 98a are positionedso as to ride on the circumference of the

cams

82 and 98 respectively. Each follower operates a microswitch which controls the opening and closing of thecontacts 82b and 9,811. The microswitch associated with cam 82 is normally closed and the microswitch associated with the'cam 98 is normally open. When the cams have been rotated so that the cam-followers fall into the notches on their respective cams'a test. cycle which lasts about two seconds is started.

Referring to Fig. 3, when the cam follower 98a falls into the notch on the cam 98, a circuit isvclosed which includes the line 100, which is connected to a power supply, the switch contact 9811', line 102, the linej30 to the transmitter unit and the coil of the relay 104 in the transmitter unit. This energizes the relay which attracts its armature 104a and disengages it from. the contact 1%41'7. The opening of the armatureand contact. adds the resistor 106 to the plate circuit of the transmitter units oscillator tube. This alters the frequency of oscillation of the transmitter oscillator in a manner which simulates the presence of an intruder in the enclosure. At the same time that this is occurring, the cam follower 82a has entered the notch on the cam 82 thereby opening its associated microswitch. This breaks the line between the relay armature 78a and the central oflice so that if the receiver unit detects the change in frequency an alarm will not be' sounded in the central ofiice. Since the test lasts for'only about 2 seconds, the protection afforded by the system is not materially decreased. However, actuation of the relay 78 will maintain the condenser 87 sufficiently charged through armature 78b and contact 78d to keep the relay 54 actuated; thereby maintaining the central office circuit closed, whichis the normal condition.

A second supervisory circuit is provided to detect a failure in the first supervisory circuit just explained. The remote possibility exists that relay 54 may be abnormally held operated and the supervision a-lforded by the first supervisory circuit will consequently be destroyed, since regardless of whether or not the relay '78 is operating the line to the central office cannot. be opened. To guard against such a possibility, a second supervisory circuit is provided which is very similar in operation to that of the first circuit. The relay 92 which is connected in the plate circuit of the tube 88 in series with the relay 54 depends for its operation upon the'normal rise and fall of plate current in the tube 88. This relay isadjusted so that it releases its armature 92a just before the plate current in the tube 88 reaches its normal minimum. When the 'armatureis released it engages the contact 92b connecting the condenser 108 to the line 99. This charges the condenser which is in the grid circuit of the tube .11) and thereby maintains the plate current of this tube at a sufficient value to maintain the relay 58 actuated. If the relay 92 is not released for several successive test periods, the capacitor 108 will discharge sufficiently through the resistor 112 to cause the plate current of the tube 110 to fall to a value which will allow the armature 58b to be released. 1 This will open the central office circuit thereby indicating a failure in the supervisory circuit; Therefunctioning. v v I I i It will be noted that the signals receivedat'the central oflice due to the presence of an intruder are different from those which are due to a malfunctioning of the circuit. When an intruder is detected, the current flowing in the central olfice circuit is increased to a value which will set off the alarm in the central ofiice. If malfunctioning is detected the central ofiice circuit is open and all current flowrin the circuit is terminated.

Provision is also made in the improved system of the present invention for a test to be conducted from the central ofiice. The supervision aiforded by the automatic tests is not entirely complete. If both'of the

relays

54 and 92 are abnormally held operated, the alarm system can become inoperative without the central ofiice being aware of the fact. Therefore, central oflice tests are conducted at the beginning of and at least once during each protected period. In order that the central ofiice test will be eifective regardless of the operation of the aforementioned relays, the central oflice test is independent of these units, and operates in the same manner in which the system will operate if an intruder is present. In order to make such a test from the central office, two conditions must be met. First, a test signal must be initiated by the transmitter unit 12and, second, the contacts 78a and 780 of the relay 78 must be connected to the centraloflice regardless of the position of the cam follower 82a. To initiate a test at the central ofiice, the current in the central ofiice circuit is increased momentarily by moving the contact 57 to cause it to engage contact 59. This puts the high voltage battery 61 in the line. This increase of current is sufficient to cause the stepping relay 46 to move the insulator wheel 46a to such a position that the contacts 46b and 460 are allowed to touch each other. This bypasses the resistor 64 in the central oflice circuit thereby decreasing the resistance of the circuit. The decreased resistance will allow the current in the central office circuit to rise to a value of 15 milliamperes. This is the first phase of the central office test and is utilized to determine if the stepping relay and the central oflice circuit are in proper operating condition. Also this test is used to calibrate the contact making meter 45 of the central ofi'ice equipment.

After this initial phase has been completed, the current in the central ofiice circuit is again briefly increased to a value which is sufiicient to cause the relay 46 to move the insulating ring 46a into its third position. Under these circumstances,,the

contacts

46b and 46c are again opened

but'the contacts

46d and 46a are closed. This connects the resistor 64 back into the central otl'ice circuit but now the relay 114 is connected in parallel with this resistor. Actuation of the relay attracts the armatures 114a and 11412 thereby bypassing the microswitch which is actuated by the cam follower 98a. This energizes the solenoid 104 in the transmitter unit and causes the transmitter to emit a signal. The operation of the armature 114a bypasses the microswitch actuated by the cam follower 82a and insures that the armature 78a and contact 78c are in the central ofiice circuit. If this system is in proper operating condition, an intruder signal is received in the central oifice. When a signal is received the current in the central ofiice circuit is again briefly increased. This actuates the changer magnet for a third time and causes the insulating ring to be returned to the position shown in Figure 2 As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within the metes and bounds of the claims or that form their functional as well as conjointly cooperative equivalents, are therefore intended to be embraced by those claims.

We claim:

l. A supervisory circuit for use with a burglar alarm system which detects the presence of an intruder by responding to the disturbance of a standing wave pattern of ultrasonic waves which comprises a first circuit connected to a remote location, said first circuit carrying a predetermined current, a second circuit connected across a portion of said first circuit, a normally open switch in said second circuit, means actuated during a disturbance of the standing wave pattern to close said switch, means for disturbing the standing wave pattern during predetermined periods, means for opening said second circuit during said periods to prevent alarm operation, and means, including said first mentioned means, responsive to a malfunctioning of the alarm system to decrease the current in said first circuit to cause alarm operation.

2. A supervisory circuit for use with a burglar alarm system which detects the presence of an intruder by responding to the disturbance of a standing wave pattern of ultrasonic waves which comprises a first circuit connected to a remote location, a first normally closed switch connected in said first circuit and when open causing an alarm, said first circuit carrying a predetermined normal current, a second circuit including a normally open switch connected across a portion of said first circuit and when closed shunting said portion of said first circuit to cause an alarm to be given, means operated during a disturbance of the standing wave pattern to close said normally open switch to give an alarm, means for disturbing the standing wave pattern during predetermined periods, means for opening said second circuit during said periods, and means responsive to the failure of operation of said first mentioned means during several of said predetermined periods to open said first switch to cause an alarm.

3. A supervisory circuit for use with a burglar alarm system which detects the presence of an intruder by responding to the disturbance of a standing wave patern of ultrasonic waves which comprises a first circuit connected to a remote location, said first circuit comprising at least a first normally closed switch and an impedance, a second circuit comprising a second normally closed switch and a normally open switch, said second circuit connected across a portion of said first circuit including said impedance, means operated during a disturbance of the standing wave pattern to close said normally open switch and shunt said impedance, means for periodically disturbing the standing wave pattern for predetermined periods, means for opening said second normally closed switch during said periods and means responsive to a failure of said first mentioned means to operate'for several of said predetermined periods to open said first normally closed switch.

4. A supervisory circuit for use with a burglar alarm system which detects the presence of an intruder by responding to the disturbance of a standing wave pattern of ultrasonic waves which comprises a first circuit connected to a remote location, said first circuit carrying a predetermined current, a second circuit shorting a portion of said first circuit, a normally open switch in said second circuit, means actuated during a disturbance of the standing wave pattern to close said switch, automatic means for disturbing the standing wave pattern during predetermined periods, means for opening said second circuit during said period, means responsive to a signal initiated at the remote location for disturbing the standing Wave pattern and means also responsive to said signal and in parallel with said third mentioned means so as to close said second circuit.

5. A supervisory circuit for use with a burglar alarm system which detects the presence of an intruder by respending to the disturbance of a standing wave pattern of ultrasonic waves which comprises a first circuit connected to a remote location, said first circuit comprising at least,

across a portion of said first circuit including said impedance, means operated during a disturbance of the standing wave pattern to close said normally open switch, means for periodically disturbing the standing Wave pattern for predetermined periods, means for opening said second normally closed switch during said period, means responsive to a signal initiated on said first circuit at the remote location for short circuiting at least part of said impedance, a relay, said last mentioned means being responsive to a second signal initiated at the remote location for opening the short circuit across the impedance and for connecting said relay across at least part of the impedance thereby energizing said relay, means responsive to the energization of said relay for disturbing the standing wave pattern and means also responsive to the energization of said relay for short circuiting said second normally closed switch.

6. A supervisory circuit for use with a burglar alarm system which detects the presence of an intruder by responding to the disturbance of a standing wave pattern of ultrasonic waves which comprises a first circuit connected to a remote location, said first circuit comprising at least a first normally closed switch and an impedance, a second circuit comprising a second normally closed switch and a normally open switch, said second circuit connected across a portion of said first circuit including said im pedancc, means operated during a disturbance of the standing wave pattern to close said normally open switch, means for periodically disturbing the standing wave pattern for predetermined periods, means for opening said second normally closed switch during said periods, an energy storing device, means responsive to the operation of said first mentioned means for supplying energy to said energy storing device, means for continuously dissipating the energy in said energy storing device and means actuated when the energy stored in the energy storing device falls below a predetermined level for opening said first normally closed switch.

7. A supervisory circuit for use with a burglar alarm system which detects the presence of an intruder by responding to the disturbance of a standing wave pattern of ultrasonic Waves which comprises a first circuit connected to a remote location, said first circuit comprising at least a first normally closed switch and an impedance, at second circuit comprising a second normally closed switch and a normally open switch, said second circuit connected across a portion of said first circuit including said impedance, means operated during a disturbance of the standing wave pattern to close said normally open switch, means for periodically disturbing the standing wave pattern for predetermined periods, means for opening said second normally closed switch during said periods, an energy storing device, means responsive to the operation of said first mentioned means for supplying energy to said energy storing device, means for continuously dissipating the energy in said energy storing device, the rate of dissipation of the energy in said energy storing device being such that the energy falls 'to a first predetermined level in the interval between each predetermined period and falls to a second predetermined energy level upon failure of oper ation of said first mentioned means for several of said predetermined periods, means responsive to said second energy level for opening said first normally closed switch, a second energy storage device, means responsive to the normal rise and fall of energy in said first mentioned energy storage device during each predetermined period for supplying energy to said second energy storage, device, means for continuously dissipating the energy in said second energy storage device, a third normally closed switch, said third normally closed switch connected in said first circuit and means actuated when the energy in said second energy ,stor-ing device falls below a predetermined minimum for operating said third norm-ally closed switch.

8. A supervisory circuit for use with a burglar alarm system which detects the presence of an intruder by responding, to the disturbance of a standing wave. pattern of ultrasonic waves which comprises a first circuitconne'cted toa remote location, said first circuit comprising at least a first normally'closed switch and an impedance, at second, circuit, comprising a second normally closed switch and a normally open switch, said second circuit connected across a portion of said first circuit including said impedance, means operated during a disturbance of the standing Wave pattern to close said normally open switch, means for periodically disturbing the standing wave pattern for predetermined periods, means for opening said second normally closed switch during said periods, an energy storing device, means responsive to the operation of said first mentioned means for supplying energy to said energy storing device, means for continuously dissipating the energy in; said energy storing device, the rate of dissipation of the energy in said energy storing device being such that the energy falls to a first predetermined level in the interval between each predetermined period and falls to a second predetermined energy level upon failure of operation of said first mentioned means for several of said predetermined periods, means responsive to said second energy evel for opening said first normally closed switch, a second energy storage device, means responsive to the normal rise and fall of energy in said first mentioned storage device during each predetermined period for supplying energy to said second energy storage device, means for continuously dissipating the energy in said second energy storage device, a third normally closed switch, said third normally closed switch connected in said first circuit, means responsive to a signal initiated on said first circuit at the remote locations for short circuiting at least part of said impedance, a relay, said last mentioned means being responsive to a second signal initiated at the remote location for opening the short circuit around the impedance and for connecting said relay across at least part of said impedance thereby energizing said relay, means responsive to the energization of said relay for disturbing the standing wave pattern and means also responsive to the energization of said solenoid for short circuiting said second normally closed switch.

9. For an alarm system in which carrier fluctuations are propagated in an enclosure and there modulated by a condition "to be detected and in which the modulations are employed to actuate a signal switch to give an alarm, supervisoryapparatus for periodically disturbing the propagation of the carrier fluctuations to simulate the condition to be detected and responsive to give a trouble signal if the. signal'switch is not actuated upon each disturbance, said supervisory apparatus comprising a first circuit, "a switch in the first circuit, means in the first circuit actuated by operation of the first circuit switch to disturb the propagation of the carrier fluctuations by the alarm system and thereby simulate the condition to be detected in the enclosure, means associated with the. first circuit switch for efiecting short interval periodic operation thereof, a second circuit, a switch in the second circuit, a trouble signal device in the, second circuit actuatable by operation of said second circuit switch, a third circuit, control tube means in the third circuit having a control electrode and an output which increases with the potential on the control electrode, relay means in the third circuit energized by a predetermined control tube output, said second circuit side of the capacitor means and adapted to dissipate therefrom at a predetermined rate potential thereon, and a switch in the fourth circuit operated by actuation of the signal switch to apply a potential to the said one side of 'the'capacitor means, whereby the second circuit switch is held unoperated and actuation of the trouble sign-a1 devices is prevented as long as the signal switch is actuated by each propagation disturbance to periodically operate '9 the fourth circuit switch and maintain a potential on the capacitor means and on the control electrode.

10. For an alarm system in which carrier fluctuations are propagated in an enclosure from a propagation source and then modulated by a condition to be detected and in which a signal switch is actuated to give an alarm by apparatus which receives the carrier fluctuations and responds to the modulations thereon, supervisory apparatus for periodically disturbing the propagation of the carrier fluctuations to simulate the condition to be detected and responsive to give a trouble signal if the signal switch is-not actuated by each disturbance, said supervisory apparatus comprising a first circuit having a switch therein, means in the first circuit connected to, the propagation source and actuated by operation of said first circuit switch to disturb the propagation of the carrier fluctuations by said source, said disturbance simulating the condition to be detected and effecting actuation of the signal switch when the alarm system is functioning properly,

means associated with the first circuit switch for effecting short interval periodic operation thereof, a second circuit having a switch therein, a trouble signal device in the second circuit actuatable by operation of said second circuit switch, a third circuit, control tube means in the third circuit having a control electrode and an output which increases with increases in potential on the control electrode, relay means in the third circuit energized to hold the second circuit switch nnoperated by a predetermined control tube output, a fourth circuit, capacitor means in the fourth circuit having one side connected to the control electrode and to by-pass means adapted to dissipate at a predetermined rate any potential on the said one side of the capacitor means,'and a switch in the fourth circuit operated by actuation of the signal switch to apply a potential to the said one side of the capacitor means, said predetermined rate of potential dissipation by the by-pass means'being selected so that if'the fourth circuit switch is not actuated upon each' periodic propagation disturbance to replenish the potential on the said one side of the capacitor means said potential, also appearing on the control electrode, decreases until the control tube output. is less than the predetermined output and the second circuit switch is operated to actuate the trouble signal device.

11. For an alarm system in which supersonic fluctuations are propagated into an enclosure from a transmitter source and then modulated by a condition to be detected in the enclosure and in which receiver apparatus adapted to receive the fluctuations responds to the modulations thereon to energize the relay means of a relay operated,

signal switch and thereby actuate alarm devices, supervisory apparatus for periodically disturbing the propagation of the fluctuations at the transmitter source to simulate the condition to be detected and responsive to give a trouble signal if the signal switch relay means is not energized by each disturbance, said supervisory apparatus means in the first circuit connected to the transmitter source and actuated by operation of the first circuit switch to disturb the propagation of the fluctuations,said alarm system receiver apparatus being capable of responding to the disturbed fluctuations to energize the signal switch relay means when the alarm system is functioning propcomprising a first circuit, a switch in the first circuit, 7

erly, means associated with the first circuit switch for effecting short interval periodic operation thereof, a sec ond circuit, a switch inthe second circuit, a trouble signal device in the second circuit actuatable by operation of said circuit switch, a third circuit, relay means in the third circuit adapted to hold the second circuit switch unoperated when energized by a predetermined current, control tube means in the third circuit having a control electrode and adapted to draw said predetermined current through said third circuit relay means when the control electrode is at a predetermined potential, a fourth circuit, capacitor means in the fourth circuit ceeding periodic disturbance and the second circuit switch.

having one side connected to the control electrode, bypass resistor means connecting the said one side of the capacitor means to a ground point, said by-pass means being adapted to dissipate at a predetermined rate potentials on the said one side of the capacitor means, a switch in the fourth circuit actuated by energizing of the signal switch relay means to apply a potential to the said one side of the capacitor means which exceeds the predetermined potential, said predetermined rate of potential dissipation being selected so that if the fourth circuit switch is not actuated upon each periodic disturbance to replenish the potential on the said one side of the capacitor means, said potential becomes less than said predetermined potential and the second circuit switch operates to actuate the trouble signal device. I

12. The combination with an alarm system in which supersonic fluctuations are propagated into an enclosure from transmitter means and then modulated by a con- 'dition to be detected in the enclosure and in which re ceiver means adapted to receive the fluctuations respond supervisory apparatus for periodically disturbing the normal operation of the transmitter means to cause the fluctuations propagated thereby to resemble fluctuations modulated by the condition to be detected and responsive to give a trouble signal if the receiver means does not respond to the fluctuations resulting from each disturbance, said alarm system having an alarm circuit, an alarm device in the alarm circuit, a signal switch in the alarm circuit operated 'by response of the receiver means to actuate the alarm device, said supervisory apparatus comprising a first circuit, a switch in the first circuit, means in the first circuit and in the transmitter means actuated by operation of the first circuit switch to briefly disturb the normal operation of the transmitter means and cause the fluctuations propagated thereby to resemble fluctuations modulated by the condition to be detected in the enclosure, said receiver means being capable of responding to fluctuations resulting from said disturbances .when the receiver means is functioning properly, means associated with the first circuit switch for effecting short interval periodic operation thereof, a second circuit, a switch in the second circuit, a trouble signal device in the second circuit actuatable by operation of said second circuit switch, a third circuit, relay means in the third circuit adapted to hold the second circuit switch unoperated when energized by a predetermined current, control tube means in the third circuit having a control electrode adapted to draw said predetermined current through said third circuit relay means when the control electrode is at a predetermined potential, a fourth circuit, capacitor means in the fourth circuit having one side connected to the control electrode, by-pass resistor means connected between the said one side of'the capacitor means and a point in the fourth circuit which is at a lower potential than the said one side, said by-pass means being adapted to dissipate at a predetermined rate potentials on the said one side of the capacitor means which exceed the potentials at said point, a switch in the fourth circuit actuated by a response of the receiver means which is capable of operating the signal switch to apply a potential to the said one side of the capacitor means which exceeds the predetermined potential, said predetermined rate of potential dissipation by the by-pass means being selected so that if the fourth circuit switch is unactuated by any periodic disturbance the potential on the said one side of the capacitor means becomes less than the predetermined potential before the occurrence of the sucoperates to actuate the trouble signal device, and said alarm circuit having an additional switch therein operated by the means effecting periodic short interval closing of the first circuit witch to render the alarm device incapable of actuation during the periodic disturbance.

' 13. For an alarm system in which carrier fluctuations are propagated in an enclosure and there'modulated by .a condition to be detected and in which the rnodulations are employed to actuate a signal switch to give an alarm, supervisory apparatus for periodically-changing the character of the propagated-fluctuations to simulate the Condition to, be detected and responsive to give a trouble signalif the signal switch is not actuated upon each periodic change, said supervisory apparatus comprising a first circuit, a switch in the first circuit, means in the first circuit actuated by operationof the first circuit switch to change the character of the propagation fluctuations to simulate the efiecton said fluctuations of the condition to be detected in the enclosure, means associated with the first ,circuit switch for effecting short interval periodic operation thereof, a second circuit, first and on the control electrode, first and second relay means in -the' third circuit energized by a predetermined control tube output, said second circuit first switch being held uncperated by energizing of the third circuit first relay means, a fourth circuit, capacitor means in the fourth circuit having one side connected to the control electrode, by-pass means connected to the said one side of the capacitor means and adapted to dissipate therefrom at a predetermined rate any potential thereon, a switch in the fourth circuit operated by actuation of the signal switch to apply potential to the said one side of the capacitor means, a fifth circuit, additional control tube means in the fifth circuit having a control electrode and an output which increases with the potential thereon, relay means in the fifth circuit energized by a predetermined additional control tube output, said second circuit second switch being held unoperated by energizing of the fifth circuit relay means, a sixth circuit, additional capacitor means in the sixth circuit having one side connected to th control electrode of the additional control tube, additional by-pass means connected to the said one side :of 'the additional capacitor means and adapted to dissipate therefrom at a certain rate any potential thereon, and a switch in the sixth circuit operated between each periodic change by thedecay in energization of the third circuit second relay means to apply a potential to the said one side of the additional capacitor means.

'14. A supervisory circuit for use with a burglar alarm system which detects the presence of an intruder by responding to a disturbance of a standing wave pattern of ultrasonic waves which comprises'a first circuit carrying a predetermined current and including a local circuit portion and a central ofiice circuit portion, said central office circuit portion including an alarm means operated upon variation of said current from said predetermined current, said local circuit portion having a predetermined impedance, a second circuit shunted across said local circuit portion and including a normally closed switch .duce a signal operating said signal actuated means thereby closing said normally open switch.

References Cited in the file of this patent UNITED STATES PATENTS Bagno May' 4, 1954 2,639,418 Sundstrom et al May 19, 1953 2,715,720

Jenkins Aug. 16, 1955