US3766537A - A.c. powered surveillance system - Google Patents

Abstract

A signaling apparatus having particular utility as a burglar alarm system is composed of a signaling circuit having an alarm signal source and a sensing circuit which trips the alarm source in the signaling circuit upon the appearance of a burglar or other condition to which the sensing circuit is sensitive. The sensing circuit includes a plurality of normally closed, serially connected switches which hold a sensing relay energized in the absense of the condition. With the appearance of the condition, the sensing relay is deenergized and a latching relay is tripped which energizes the alarm signal source. To prevent the latching relay from being tripped whenever power to the sensing relay is initially turned on or subsequently dips, a sequencing relay is interposed between the sensing relay and latching relay and insures that the sensing relay is energized first. Since the sensing relay is normally energized, there is continual supervision of the sensing circuit. The apparatus also has failsafe provisions and the signaling circuit is capable of providing a test signal each time the apparatus is turned on.

Description

United States Patent [191 MacFarlane Oct. 16, 1973 A.C. POWERED SURVEILLANCE SYSTEM [75] Inventor: John MacFarlane, Avon, Conn.

[73] Assignee: The Theodore D. Bross Line Construction Corporation, Bloomfield, Conn.

[22] Filed: May 3, 1971 [21] Appl. No.: 139,714

[52] US. Cl. 340/276, 340/274 [51] Int. Cl. G08b 13/08 [58] Field of Search 340/276, 274; 116/75, 86

[56] References Cited UNITED STATES PATENTS 3,200,393 8/1965 Worley 340/276 2,493,576 l/l950 Foss 340/274 Primary Examiner-John W. Caldwell Assistant Examiner-Glen R. Swann, llI Attorney-McCormick, Paulding & Huber [5 7] ABSTRACT A signaling apparatus having particular utility as a burglar alarm system is composed of a signaling circuit having an alarm signal source and a sensing circuit which trips the alarm source in the signaling circuit upon the appearance of a burglar or other condition to which the sensing circuit is sensitive. The sensing circuit includes a plurality of normally closed, serially connected switches which hold a sensing relay energized in the absense of the condition. With the appearance of the condition, the sensing relay is deenergized and a latching relay is tripped which energizes the alarm signal source. To prevent the latching relay from being tripped whenever power to the sensing relay is initially turned on or subsequently dips, a sequencing relay is interposed between the sensing relay and latching relay and insures that the sensing relay is energized first. Since the sensing relay is normally energized, there is continual supervision of the sensing circuit. The apparatus also has fail-safe provisions and the signaling circuit is capable of providing a test signal each time the apparatus is turned on.

15 Claims, 1 Drawing Figure PILOT LIGHT CRI 46 }L rom 3 MINUTE DELAY 50 V 42 ALARM LIGHT A! /44 5 TDR L ALARM BEL 52 1 48 |a,-L l m L 24 I6 26 26 2e SENSING RELAY CR1 so P Q SEQUENCING RELAY 28 V 34 32 5 3 36 Q LATCHING RELAY W t CR 3 PATENIEDUBI 16 I915 3.766; 537

r PILOT LIGHT 3 MINUTE DELAY 5O 42 m I l ALARM LIGHT I SENSING RELAY (:R so CW2 SEQUENCING RELAY 34 32 3s m A CR-3 LATCHING RELAY l INVENTOR.

JOHN MACFARLANE ATTORNEYS 1 A.C. POWERED SURVEILLANCE SYSTEM BACKGROUND OF THE INVENTION The present invention relates to a signaling apparatus which provides a visual, audio or other type of signal upon the detection of a condition to which the apparatus is sensitized. The apparatus is specially suited to the function of a burglar alarm system and has self-testing and continual supervision features.

In apparatus which is designed to detect a particular condition that occurs with random or unscheduled frequency over extended periods oftime, it is desirable that the systems be continually supervised and fail-safe. It is also desirable that such systems not require extensive maintenance or frequent servicing during the period of activation. The specifications that a system be continually supervised and, at the same time, not require frequent servicing are, for practical purposes, conflicting prerequisites; however, these prerequisites are frequently demanded in many types of warning systems, especially in burglar alarm systems which lie dormant for long periods of time and yet must be prepared to give an alarm signal when the security of the area under supervision is first broken.

In many burglar alarm systems, it is customary to employ batteries for energizing the system. While batteries provide a reliable source of electrical power on a short term basis, they must be recharged or replaced on occasion for extended reliability of the system. Where reasonably reliable line power is available, the maintenance aspects of the battery-operated systems can be eliminated.

Where it is desired to combine the continual supervision feature with the low maintenance feature in an alarm system, reliable line power is also an attractive alternative as a power source because continual supervision normally requires continual energization of a sensing circuit. In systems utilizing batteries, the continual energization results in a more rapid discharge of the batteries. If the sensing circuit is not continually energized so that power consumption is avoided, the supervision or monitoring features of the system are lost. It is therefore desirable to utilize line power for a burglar alarm where low maintenance and continual supervision features are desired.

One problem associated with line power in a supervised alarm system is that the system must be capable of discriminating between the actual detection of a condition to which the system is sensitive and a power failure or fluctuation in the voltage level of the power since both situations are accompanied by loss of energization in the sensing circuits. Only the former situation, the actual detection, should set off the alarm.

Accordingly, it is a general object of the present invention to provide a signaling apparatus having low maintenance, fail-safe and supervisory features and which at the same time can distinguish between the detection of a selected condition and a power failure.

SUMMARY OF THE INVENTION The present invention resides in a signaling apparatus comprised of an electrical sensing circuit and signaling circuit. The sensing circuit has a normally closed sensing switch sensitive to and opened by a condition to be detected and a sensing means connected with and electrically energized through the sensing switch. The signaling circuit is provided with an alarm signal source such as a light or alarm bell which is actuated by the sensing circuit when the sensing switch is opened and the sensing means is de-energized. Latching means is connected between the sensing means. and the alarm signal source and is responsive to the sensing means for actuating the alarm signal source subsequent to the deenergization of the sensing means. Sequencing means is provided for arming the latching means after energization of the sensing means and prevents the latching means from tripping the alarm signal source when the signaling apparatus is first turned on by switch means electrically connected with the signaling and sensing circuits.

The sequencing means is utilized to provide a test signal each time the signaling apparatus is energized. The energization of the sensing means through the normally closed sensing switches provides continual monitoring or supervision of the signaling apparatus and the alarm signal source is actuated upon a failure of either the sensing means or sequencing means. The signaling apparatus, therefore, has testing, monitoring and fail-safe features.

BRIEF DESCRIPTION OF THE DRAWING The drawing is an electrical diagram showing the signaling and sensing circuits of a preferred embodiment of the signaling apparatus of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The signaling apparatus of the present invention having testing, monitoring and fail-safe features is shown in the drawing in a preferred embodiment. While the invention is suitable for other uses, the signaling apparatus has particularly utility as a burglar alarm system and hence is shown in the drawing and described below in such a form to more clearly present its several features.

The signaling apparatus, generally designated 10, is energized by a power source 12 which in its most common form would be a 110 volt or 220 volt ac power supply line such as that found in most buildings or areas which are secured by an alarm system. The signaling apparatus 10 is comprised of a high voltage signaling circuit 14 connected to the power supply 12 and a low voltage sensing circuit 16 coupled to the signaling circuit 14 by means of an ac step-down transformer 18. The transformer reduces the excitation voltage of the signaling circuit to, for example, 24 volts across the secondary winding which excites the sensing circuit 16. A master control switch 20 in the high voltage circuit 14 is utilized to turn the signaling apparatus 10 on and off by connecting the power source 12 directly to the signaling circuit 14 and indirectly to the sensing circuit 16 through the transformer 18. As shown, the control switch 20 is a single-pole,single-throw switch 20 which may be key operated so that the system can be either locked on or off by security personnel. The switch 20 serves as the only manual control for the alarm system and consequently all other features of the system such as testing, monitoring and signaling failures are automatically controlled.

With the control switch 20 closed, a pilot light 22 is energized to indicate that the signaling apparatus 10 is turned on. In this condition, power is transmitted through the transformer 18 to the low voltage sensing circuit 16 and energizes a sensing relay 24, designated CR-l, through a plurality of serially connected sensing switches 26. The sensing switches 26 are normally closed and so arranged in a building as to be opened in the presence of a condition to be detected. For example, in the burglar alarm system, the switches 26 are actuated to the open position whenever a door or window of a building is opened. It will thus be apparent that the switches 26 may be mechanically actuated by a window or a door, or that other devices such as photoelectric cells and similar detection devices might be used. The term sensing switch is intended to cover such devices.

With each of the sensing switches 26 in the closed position indicating a secure condition, the sensing relay 24 is energized. The relay 24 is provided with a set of normally open contacts 28 which are connected in series with a sequencing relay 30 designated CR-2. When the sensing relay 24 is energized, contacts 28 close and energize the sequencing relay 30. The sequencing relay 30 has a pair of normally open, latching contacts 32 which close upon energization of the sequencing relay to hold the sequencing relay in the energized condition after it is intially energized through the contacts 28. The contacts 32 are connected in series with a latching relay 34, designated CR-3, through a set of normally closed contacts 36 forming a part of the sensing relay 24. The contacts 32 of the sequencing relay 30 serve the function of arming the latching relay 34 subsequent to the energization of the sensing relay 24 through the switches 26.

During power up operations, the sensing relay 24 is energized first and in turn closes contacts 28 and opens contacts 36; contacts 28 and 36 being transfer contacts whereby contacts 36 must open before contacts 28 close. The sequencing relay 30 is not energized until after the sensing relay has been energized and therefore contacts 36 are opened before contacts 32 are closed. Accordingly, the latching relay 34 is not energized when power is first turned on due to the delayed response of the sequencing relay contacts 32.

During normal operation (power on), the deenergization of the sensing relay 24 due to the opening of one of the sensing switches 26 permits contacts 36 to return to a closed position to energize the latching relay 34. The relay 34 has one set of latching contacts 38 which hold relay 34 energized after one of the sensing switches 26 is opened and another set of normally opened contacts 40 connected in the high voltage signaling circuit 14 in series with an alarm signal source such as the alarm light 42 or the alarm bell 44. Consequently, whenever a sensing switch 26 is opened during power on operation, contacts 38 and 40 of latching relay 34 close and the alarm signal source is energized. The alarm signal source remains energized even though the sensing switch which caused the contacts 40 to close is returned to its normally closed position. It will be apparent therefore, that even if a burglar realizes that he has set off the alarm signal, he cannot deenergize the alarm source by reclosing the switch 26 since the relay 34 is latched by contacts 38.

The alarm light 42 and the alarm bell 44 are connected in parallel with each other and with a time-delay relay 46 and all of these devices are energized by the contacts 40. The time-delay relay 46 has a set of normally closed contacts 48 connected in series with the alarm bell 44 and after the relay is energized for a delay period of, for example, three minutes, the contacts 48 open and de-energize the alarm bell 44. The time-delay relay 46 thereby permits the alarm bell 44 to provide an alarm sound of sufficient duration to warn security personnel that a burglar has tripped one of the sensing switches 26. The bell then shuts off, but the alarm light 42 remains energized to provide a continuous visual indication that the signaling apparatus has been tripped.

The signaling apparatus 10 is shut off and reset by opening and closing the key control switch 20. When the switch 20 is opened, the sensing relay 24, the sequencing relay 30 and the latching relay 34 are deenergized in conjunction with the alarm light 42 and alarm bell 44. At this point, all of the elements of the signaling and sensing circuits are returned to the original conditions observed prior to power-up operations. Consequently, when the control switch 20 is reclosed, sensing relay 24 and sequencing relay 30 are reenergized in that order and arm the latching relay 34 as described above.

The above description details the normal operation of the signaling apparatus in detecting an unauthorized entry or breaking into a secured area. The automatic testing and supervising functions performed by the signaling apparatus 10 will now be described.

The signaling apparatus 10 automatically provides a test signal each time the control switch 20 is closed or power is reapplied to the signaling apparatus. The test signal consists of a momentary operation of the alarm light 42 and the alarm bell 44, and if the apparatus is working properly, the alarm bell and alarm light are shut off after the momentary operation. If the signaling apparatus is not working properly, the alarm bell and alarm light continue to operate and thereby indicate a failure within the apparatus.

As mentioned above, the alarm light 42, the alarm bell 44,and the time-delay relay 46 are all turned on by the normally open contacts 40 of the latching relay 34 when the sensing switches 26 are opened. In addition, however, a set of normally closed contacts 50 forming a part of the sensing relay 24 and another set of normally closed contacts 52 forming a part of the sequencing relay 30 are connected in parallel with the contacts 40 and each of these is also capable of energizing the alarm light and alarm bell. Before power is applied to the signaling circuit 14 and sensing circuit 16 through the control switch 20, neither the sensing relay 24 nor the sequencing relay 30 is energized and therefore contacts 50 and 52 are in the normally closed positions. When the switch 20 is closed, power is applied to both the alarm light 42 and the alarm bell 44 until the sequencing relay 30 is energized to open contacts 52 since the energization of the sequencing relay 30 is delayed by the normally open contacts 28 of the sensing relay 24. During this brief delay the alarm light 42 remains on and the alarm bell 44 is sounded to indicate to security personnel that the apparatus is operative.

If for any reason the sensing relay 24 fails to operate, contacts 50 remain closed, the alarm light continues to burn and the alarm bell rings until the time-delay relay 46 opens contacts 48. Similarly, if the sequencing relay 30 fails to operate, contacts 52 remain closed and the alarm light and the alarm bell continue to function beyond the momentary test period normally provided by the sequencing relay 30. The signaling apparatus, therefore, automatically provides its own test signal each time the control switch 20 is closed or whenever power is returned to the signaling and sensing circuits.

The signaling apparatus also monitors itself after it is turned on and provides a warning signal through the alarm light 42 or alarm bell 44 in the event that a failure occurs in one of the components. The apparatus 10, therefore, supervises itself after power is turned on and fails safe or gives a break indication by energizing the alarm signal source.

To provide these supervising and fail-safe features after the apparatus is turned on and the testing operation is completed, the sensing relay 24 is continuously energized through the normally closed sensing switches 26 and the sequencing relay 30 is continuously energized through the contacts 28. If for any reason the sensing relay 24 fails, the contacts 50 close and energize the alarm sources 42 and 44 to indicate the failure. The alarm sources, therefore, provide security personnel with an indication that the system is not operating properly by providing a break indication when the sensing relay fails; the indication being in the form of a stored signal as provided by light 42 and an audible warning provided by alarm 44 and being of duration determined by time delay relay 46.

In the same manner, if the sequencing relay 30 fails, the contacts 52 close and energize the alarm light and bell. It should also be noted that a failure of the transformer 18 results in the de-energization of both the sensing relay 24 and the sequencing relay 30 so that an alarm is sounded in this case as well. A failure of the latching relay 34 does not produce an immediate warning signal; however, the apparatus with a failed latching relay will continue to operate and produce a warning signal whenever a sensing switch 26 is opened since the de-energization of the sensing relay 24 closes the set of contacts 50 which energize the alarm signal source. Thus, when the latching relay 34 fails, only the latching feature of the alarm system is lost. The result is that an intruder who recloses one of the opened sensing switches can shut off the alarm signal.

It will thus be seen that the signaling apparatus 10 provides an alarm signal whenever one of the sensing switches 26 is opened and the apparatus has both testing, supervising and fail-safe features. The testing feature is automatically provided each time the apparatus is energized and does not require a special testing switch. The supervising feature is also automatic and the apparatus does not sound the alarm after a power failure because the sequencing relay renders the apparatus capable of distinguishing between the opening of a sensing switch and a failure of the power source. Due to the capability of distinguishing between such conditions, itis possible to employ 'a simple single-pole, single-throw switch for activating and deactivating the signaling apparatus.

While the signaling apparatus has been described in a preferred embodiment, it should be understood that various modifications and substitutions can be had without departing from the spirit of the invention. For example, although the sequencing relay is operated by the sensing relay contacts 28 to provide a delayed signal for arming the latching relay 34, the relay 30 could be replaced by a time-delay relay connected directly across the secondary winding of the transformer 18 without employing the sensing relay contacts 28 or the latching characteristics of the relay 30. In addition, the sequencing relay 30 and the latching relay 34 together with contacts 28, 32, 36, 38 need not be operated at low voltage in the sensing circuit 16 but might be located in the signaling circuit 14 and operated at normal supply voltages. Although the sensing circuit i6 is shown to operate on ac power from the transformer 18, the transformer could be eliminated or an ac-to-dc converter could be utilized in place of the transformer so that the sensing circuit 16 could operate on direct current. Accordingly, the present invention has been described in a preferred embodiment by way of illustration rather than limitation.

I claim:

1. A surveillance system comprising:

condition responsive means, said condition responsive means including at least first switch means, said first switch means changing state upon establishment of a predetermined condition in an area under surveillance;

electrical power supply means;

means for energizing the system by connecting said power supply means thereto;

sensing means responsive to the state of said condition responsive means, said sensing means includ-v ing first solenoid operated relay means having a plurality of contacts, the solenoid of said first relay means being energized from said power supply means through said first switch means;

alarm means;

latching means for supplying current from said power supply means to said alarm means, said latching means being energized via a first pair of contacts of said sensing means first relay means; and self-latching sequencing means for arming said latching means, said sequencing means being energized from said power supply means via a second pair of contacts of said first relay means and establishing a circuit between said power supply means and a first contact of said first pair of sensing means first relay means contacts whereby the change of state of said first switch means will change the energization state of said sensing means first relay means only to cause energization of said alarm means via said armed latching means and whereby a momentary interruption of power from said power supply means will cause deenergization of said sequencing means and said alarm means will not be energized upon resumption of the application of power.

2. The surveillance system of claim 1 wherein said sensing means first relay means is energized through said first switching means upon connection of the system to the power supply means and wherein said sequencing means is energized to arm said latching means subsequent to energization of said sensing means.

3. The surveillance system of claim 2 further comprising:

first actuating means for said alarm means, said first actuating means applying power to said alarm means upon operation of said energizing means to connect power to the system, said first actuating means being responsive to energization of said se quencing means for disrupting the supply of power from said power supply means to said alarm means.

4. The surveillance system as defined in claim 3 wherein the sequencing means comprises a sequencing relay having a first set of contacts connected with the latching means and normally open in the deenergized state of the sequencing relay; and wherein said first actuating means comprises a second set of contacts in the sequencing relay, the second set of sequencing relay contacts being normally closed in the deenergized state of the sequencing relay.

5. The surveillance system as defined in claim 2 wherein said alarm means includes alarm signal generating means and first and second sets of alarm signal generating means energizing contacts, each set of alarm signal generating means energizing contacts being connected with the alarm signal generating means and being connected in parallel with each other, the first set of alarm signal generating means energizing contacts being closed by the deenergization of the sensing means and the second set of alarm signal generating means energizing contacts being closed by the energization of the latching means.

6. The surveillance system as defined in claim 5 wherein the alarm means further includes a third set of contacts connected in parallel with the first and second sets of alarm signal generating means energizing contacts, the third set of contacts being opened by the sequencing means with the arming of the latching means.

7. The surveillance system as defined in claim 6 wherein the sensing means is a relay including the first set of alarm signal generating means energizing contacts; the latching means is a latching relay including the second set of alarm signal generating means energizing contacts and the sequencing means is a relay including said third set of contacts.

8. A signaling apparatus comprising:

an electrical sensing circuit having a normally closed sensing switch sensitive to and opened by a condition to be detected and sensing means connected with and electrically energized through the sensing switch;

a signaling circuit having an alarm signal source;

latching means connected between the sensing means and the alarm signal source and responsive to deenergization of the sensing means for actuating the alarm signal source in the signaling circuit subsequent to a deenergization of the sensing means;

switch means electrically connected with the signaling and sensing circuits for energizing the circuits; and

sequencing means connected to and responsive to the sensing means for arming the latching means subsequent to the energization of the sensing means.

9. A signaling apparatus as defined in claim 8 wherein the sequencing means comprises a relay responsive to the sensing means and having a set of latching contacts.

10. A signaling apparatus as defined in claim 8 wherein the latching means comprises a latching relay.

11. A signaling apparatus as defined in claim 8 wherein the switch means consists of a single-pole, single-throw switch connected to the signaling circuit and the sensing circuit.

12. A signal apparatus as defined in claim 8 wherein the signal circuit is a high voltage circuit and the sensing circuit is a low voltage circuit and wherein power transfer means is connected between the signal and sensing circuits.

13. A burglar alarm apparatus comprising:

an alarm signal circuit having an alarm signal source;

a sensing circuit having at least one normally closed sensing switch and a sensing relay energized through the sensing switch, the sensing relay having at least one set of normally closed contacts; single-throw control switch connected to energize each of the circuits from an electrical power source; sequencing relay connected in one of the circuits and having a first set of normally closed contacts and a second set of normally open contacts, said first set of sequencing relay normally closed contacts being connected serially in the signaling circuit with the alarm signal source, the first and second sets of sequencing relay contacts being actuated by the sequencing relay in a sequence with and subsequent to the energization of the sensing relay in the sensing circuit; and

a latching relay armed by the second set of normally opened contacts of the sequencing relay and serially connected in one of the circuits with the said one set of normally closed contacts of the sensing relay, the latching relay also having a set of normally open contacts connected serially with the alarm signal source and in parallel with the normally closed contacts of the sequencing relay.

14. A burglar alarm apparatus as defined in claim 13 wherein the sensing relay includes a set of normally open contacts serially connected in one of the circuits with the sequencing relay and a second set of normally closed contacts connected serially with the alarm signal source in the signaling circuit and in parallel with the normally open contacts of the latching relay and the normally closed contacts of the sequencing relay.

15. A burglar alarm apparatus as defined in claim 13 wherein a time delay relay having a set of normally closed contacts connecting the alarm signal source in series with the normally open contacts of the latching relay and in series with the normally closed contacts of the sequencing relay is connected in the alarm signal circuit in parallel with the alarm signal source and contacts of the time delay relay.

Claims (15)

1. A surveillance system comprising: condition responsive means, said condition responsive means including at least first switch means, said first switch means changing state upon establishment of a predetermined condition in an area under surveillance; electrical power supply means; means for energizing the system by connecting said power supply means thereto; sensing means responsive to the state of said condition responsive means, said sensing means including first solenoid operated relay means having a plurality of contacts, the solenoid of said first relay means being energized from said power supply means through said first switch means; alarm means; latching means for supplying current from said power supply means to said alarm means, said latching means being energized via a first pair of contacts of said sensing means first relay means; and self-latching sequencing means for arming said latching means, said sequencing means being energized from said power supply means via a second pair of contacts of said first relay means and establishing a circuit between said power supply means and a first contact of said first pair of sensing means first relay means contacts whereby the change of state of said first switch means will change the energization state of said sensing means first relay means only to cause energization of said alarm means via said armed latching means and whereby a momentary interruption of power from said power supply means will cause deenergization of said sequencing means and said alarm means will not be energized upon resumption of the application of power.

2. The surveillance system of claim 1 wherein said sensing means first relay means is energized through said first switching means upon connection of the system to the power supply means and wherein said sequencing means is energized to arm said latching means subsequent to energization of said sensing means.

3. The surveillance system of claim 2 further comprising: first actuating means for said alarm means, said first actuating means applying power to said alarm means upon operation of said energizing means to connect power to the system, said first actuating means being responsive to energization of said sequencing means for disrupting the supply of power from said power supply means to said alarm means.

4. The surveillance system as defined in claim 3 wherein the sequencing means comprises a sequencing relay having a first set of contacts connected with the latching means and normally open in the deenergized state of the sequencing relay; and wherein said first actuating means comprises a second set of contacts in the sequencing relay, the second set of sequencing relay contacts being normally closed in the deenergized state of the sequencing relay.

5. The surveillance system as defined in claim 2 wherein said alarm means includes alarm signal generating means and first and second sets of alarm signal generating means energizing contacts, each set of alarm signal generating means energizing contacts being connected with the alarm signal generating means and being connected in parallel with each other, the first set of alarm signal generating means energizing contacts being closed by the deenergization of the sensing means and the second set of alarm signal generating means energizing contacts being closed by the energization of the latching means.

6. The surveillance system as defined in claim 5 wherein the alarm means further includes a third set of contacts connected in parallel with the first and second sets of alarm signal generating means energizing contacts, the third set of contacts being opened by the sequencing means with the arming of the latching means.

7. The surveillance system as defined in claim 6 wherein the sensing means is a relay including the first set of alarm signal generating means energizing contacts; the latching means is a latching relay including the second set of alarm signal generating means energizing contacts and the sequencing means is a relay including said third set of contacts.

8. A signaling apparatus comprising: an electrical sensing circuit having a normally closed sensing switch sensitive to and opened by a condition to be detected and sensing means connected with and electrically energized through the sensing switch; a signaling circuit having an alarm signal source; latching means connected between the sensing means and the alarm signal source and responsive to deenergization of the sensiNg means for actuating the alarm signal source in the signaling circuit subsequent to a deenergization of the sensing means; switch means electrically connected with the signaling and sensing circuits for energizing the circuits; and sequencing means connected to and responsive to the sensing means for arming the latching means subsequent to the energization of the sensing means.

9. A signaling apparatus as defined in claim 8 wherein the sequencing means comprises a relay responsive to the sensing means and having a set of latching contacts.

10. A signaling apparatus as defined in claim 8 wherein the latching means comprises a latching relay.

11. A signaling apparatus as defined in claim 8 wherein the switch means consists of a single-pole, single-throw switch connected to the signaling circuit and the sensing circuit.

12. A signal apparatus as defined in claim 8 wherein the signal circuit is a high voltage circuit and the sensing circuit is a low voltage circuit and wherein power transfer means is connected between the signal and sensing circuits.

13. A burglar alarm apparatus comprising: an alarm signal circuit having an alarm signal source; a sensing circuit having at least one normally closed sensing switch and a sensing relay energized through the sensing switch, the sensing relay having at least one set of normally closed contacts; a single-throw control switch connected to energize each of the circuits from an electrical power source; a sequencing relay connected in one of the circuits and having a first set of normally closed contacts and a second set of normally open contacts, said first set of sequencing relay normally closed contacts being connected serially in the signaling circuit with the alarm signal source, the first and second sets of sequencing relay contacts being actuated by the sequencing relay in a sequence with and subsequent to the energization of the sensing relay in the sensing circuit; and a latching relay armed by the second set of normally opened contacts of the sequencing relay and serially connected in one of the circuits with the said one set of normally closed contacts of the sensing relay, the latching relay also having a set of normally open contacts connected serially with the alarm signal source and in parallel with the normally closed contacts of the sequencing relay.

14. A burglar alarm apparatus as defined in claim 13 wherein the sensing relay includes a set of normally open contacts serially connected in one of the circuits with the sequencing relay and a second set of normally closed contacts connected serially with the alarm signal source in the signaling circuit and in parallel with the normally open contacts of the latching relay and the normally closed contacts of the sequencing relay.

15. A burglar alarm apparatus as defined in claim 13 wherein a time delay relay having a set of normally closed contacts connecting the alarm signal source in series with the normally open contacts of the latching relay and in series with the normally closed contacts of the sequencing relay is connected in the alarm signal circuit in parallel with the alarm signal source and contacts of the time delay relay.

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