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Publication numberUS2943304 A
Publication typeGrant
Publication dateJun 28, 1960
Filing dateJul 10, 1957
Priority dateJul 10, 1957
Publication numberUS 2943304 A, US 2943304A, US-A-2943304, US2943304 A, US2943304A
InventorsSchmidt Kenneth H
Original AssigneeMosler Res Products Inc
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Security alarm system with remotely operative test circuit
US 2943304 A
Abstract  available in
Previous page
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Claims  available in
Description  (OCR text may contain errors)

June 28, 1960 K. H. SCHMIDT 2,943,304

SECURITY ALRM SYSTEM WITH REMOTELY OPERATIVE TEST CIRCUIT Filed July 10, 1957 B Q e ATTORN Y United States Pate-nt SECURITY ALARM SYSTEM lWITH REMOTEL OPERATIVE TEST CIRCUIT Kenneth H. Schmidt, Danbury, Conn., assigner to Mosler Research Products, Inc., Danbury, Coun., a corporation of Delaware liletlV July 10, 1957, Ser.` No. 670,998

7 Claims. (Cl. 340-214) My invention relates broadly to security alarm systems, and more particular-ly to-a'testing circuit for remotely checking the condition of operation of such systems.

This invention pertains to security alarm systems of the class set forth in my copending application Serial No. 670,999 led July 10, 1957, for Security Alarm System.

One of the objects of my invention` is to provide a security alarm system `with a built-in test circuit for checking the operation of the system.

Another object of my invention is to provide a test circuit for security alarm systems which enables an operator at a remote location to test the operation of the system in the protected area which is remotely removed from av guard station.

A further object of my invention is toV provide a tes't circuit for security alarm :systems which simulates the presence of an intruder in the protected area for operating the system in similitude for indicating whether or not the system is operating in protective condition.

lOther and further objects of my invention are set forth more fully in the specification hereinafter following by referenceito the accompanying drawings, in which:

Fig. l is a schematic view showing a typical installation protected by the security alarm system of my invention;


Fig. 2 is a circuit diagram schematically showing the application of my invention to a transistorized capacityresponsive alarm system and yillustrating theV remotely operative test circuit of my invention.

My Vinvention is directed to the construction of an electronic Security alarm system in which the objects under Vprotection are connected in series, and form an antenna system, and in which a test circuit is associated with this antenna system in such a way as to simulate the presence of an intruder in the protected area when the test circuit is energized. The test circuit is operated from a remotely located guard station so that the guard at that -station can determine if the security system is operating effectively.

The system operates on an electromagnetic principle. A transistor oscillator, by means of the resonant antenna system, radiates radio frequency (RF) energy into the area surrounding the antenna system, thus setting up an electromagnetic field of stored RF energy.

An ultra-sensitive alarm relay circuitY connected to the antenna resonating circuit through a detector circuit is balanced for the 'particular antenna system' 'which has a test cricuit member associated with it. The presence of any additional body or object inthe electromagneticy field will upset the balance ,of the alarm relay circuit, thus sending in an alarm, since' the amount of RF energy l stored in the field and the capacity of the field has been l. tors are energized through a relay controlled by theVV ICC ` balanced alarm relay. The balanced alarm relay is of the self-resetting type so thatAthe alarm indicators are deenergized when the test circuit is deenergized.

In referring to the figures in more detail, similar nu-V tuning circuit in cabinet 1 by antenna connecting coaxial lead 5; and alarm indicator housing 6 which contains the alarm indicators, such as.a buzzer and a light, alarm silencer switch, system test switch, and a battery as a selfcontained power source for the alarm indicators. alarm indicator housing 6 is connected to cabinet 1 by conductors running through connecting conduit 7. Safe 3, file cabinet 2, and' cabinet` 1, of the antenna system, are insulated from ground by insulating blocks 8. Grounding conductor 9, insulated from cabinet 1, suppliesy the grounding requirements for the system.

YIn Fig. 2 I, have shown the electrical schematic diagram of the transistorized capacity alarm system incorporating the system test Ycircuit of my invention. Power source 10, an independent battery power source contained within cabinet housing 1, energizes the transistor-oscillator circuit through Day-Night switch 11, power buss 12, oscillator transformer primary winding 13, andbase bias resistor 14. Oscillator tank capacitance 15 and secondary winding y16-of the oscillator transformer form the tank circuit for the oscillatorcircuit anddetermine the radio frequency (RF) output of the oscillator circuit. i The tank circuit is coupled to type NPN oscillatorv transistor 17a throughV oscillator transformer primary winding 13 ,and coupling capacitor 18. By-pass capacitor 19 isconnected between power buss 12 and ground. to remove any A.C. pickup from said power buss. The RF output from the oscillator transistor base 17b is coupled through coupling capacitor 20 and conductor Zto the antenna tuning cir.- cuit which consists lof tuning capacitor 21 inA parallel with tapped primary winding 22 of detector'transformer 23. The antenna system whichconsists of electrically conductive housing 1 coupled by means of desensitizing capacitor 25, and objects 26 to be protected (example:

tile cabinet 2 andsafe 3 in Fig. l) connected by means.

of antenna connecting coaxial lead 5, to internal antenna connecting conductor 5 which is connected to a tap on detector transformer tapped primary windingrZZ. The detector circuit contains detection transistor 27, which is a type NPN transistor, the base 23a of which* is connected to secondary winding 29 of detector transformer 23, thus inductively coupling the detector circuit to the balanced antennasystem. Transistor collector member ZSbis connected to power buss 12 and emitter member 28e is connected to 'ground buss 9 through tuning meter 30. The outputof the detector circuit, fromemitter member V280,' is VconnectedV to ground through lay-'passi capacitor 31 and'to'coiljl 32 of balanced alarm relay 33 through compensation coupling capacitor 34. For amore thorough explanation of thev basic theory of operation of the'preceding' circuit, refer to my copending application Seriall No. 670,999,

Alarm System. f

Balanced alarm 4relay 3-3 responds to very slightchangesin current of the magnitude of two micro-amperes- Patented June 28, 1960` The filed July 10, A1957,'fo'r Security? is connected lto ground buss 9 and both relay contact points 36 are normally open and connected together.

The circuit of slave relay 37 consists of slave relay coil 38 Vand voltage drop resistor 39 connected in series across groimd buss 9 and power buss 12, respectively. This necessarily puts slave relay 37 in a normally energized state when switch 11 is in the Night position. Alarm relay common contact points 36 are connected between the junction of voltage drop resistor 39 and slave relay coil 38. With this circuitry, whenever the balance of the alarm relay circuit is disturbed, the relay is energized and movable contact arm 35 grounds one of common contact points 36 which puts a ground on both ends of slave relay coil 38, thus deenergizing the normally energized slave relay 37. This causes slave relay contact arm 40 to move from the normally closed contact point 41 to the normally open contact point 42, thus activating an alarm remotely located in alarm indicator housing 6. Cabinet 1 also contains test relay 43 and test member or coil 4S disposed around, but not in contact with, internal antenna connecting conductor One end of test coil 45 is an open circuit. That is to say, the coil or member 45 is spatially related to the internal antenna conductor 5. The other end of test coil 45 is connected to test relay movable contact member 46 which is in contact with open relay fixed contact point or stop 47 when the test relay is in the deenergized state. Normally open test relay fixed contact point 43 is connected to ground buss 9. Connecting conductors 49 and 5t) disposed in conduit 7 connect test relay coil 44 through test switch 51 to relay activating power source S2. Test switch 51 and power source 52, which may be a battery, are both remotely located in alarm indicator housing 6. When test switch 51 is thrown, test relay 43` is energized, moving test relay movable contact member 46 into contact with the grounded normally open test relay contact point 4S. This connects open test coil 45 in a series circuit to ground which will change the current in the balanced alarm relay circuit since the balance of the antenna system has been disturbed and cause an alarm, since this grounded coil in proximity to the antenna system lhas added a small amount of capacity to the antenna in exactly the same manner as an intruder approaching a safe or le cabinet in the antenna system. With this testing arrangement an operator at the alarm housing 6 remotely located from the antenna system can test the systems operation without being in the immediate vicinity of the antenna system. Sincel the alarm relay is of the self-resetting type it will reset itself after the test switch 51 is returned to its normal position.

Alarm indicator housing 6 also contains indicator battery power source 58, and indicator light 53, and buzzer oraudible alarm 54 connected in parallel. Indicator battery power source S8 is connected to slave relay movable contact arm member 41 by conductor S9 in conduit 7. The indicators are then activated by slave relay 37 when alarm relay 33 becomes unbalanced. Both indicators indicate when the system becomes unbalanced and goes into alann since they are connected, by conductor 5S in conduit 7, to normally open slave relay contact 42. The buzzer or audible alarm 54 may be silenced by means of silencer switch 56 when the system is in an alarm condition, but the indicator light will not extinguish until the system is rebalanced and operating properly. For failsafe protection, if the silencer switch has been thrown, it must be returned to the normal position when the system is rebalanced or the audible alarm indicator 54 will sound, since the silencer switch is wired to the normally closed contact point 41 of` slaverelay37 by conductor 57.

Unauthorized opening of cabinet 1 is prevented While switch 11 is in the Night position since the cabinet housing is. connected into the balancedantenna system. This being the case, if an intruder touched the cabinet he would change the amount` of radio frequency energyV 4 activating the relay and resulting in the alarm indicator being energized.

When switch 11 is in the Day position slave relay 37 is deenergized and slave relay movable contact member 41 is in contact with the normally open contact point 42. ln this state, the alarm indicators are energized, so that during non-operating periods alarm silencer switch 56 must be moved to the normally open position, resulting in the audible alarm 54 being silenced. Visual indicator 53 will remain energized during non-operating periods.

To protect cabinet 1 from unauthorized opening during the Day periods of system non-operation, tamper switch 60 is disposed in alarm energizing conductor 59 and arranged to make contact between this line and conductor 57 if cabinet 1 is opened. Since silencer switch 56 is in the normally open position and thus connected to conductor 57, if cabinet 1 is opened a closed circuit between power source 58 and audible alarm 54 results and this alarm is energized whilevisual alarm 53 is deenergized.

Alarm indicator housing 6 is associated with tamper switch 61 to prevent any unauthorized opening of this housing during both operating and non-operating periods or during both Night and Day positions of switch 11. Tamper switch 61 is a double-pole, double-throw switch with both movable members mechanically associated with housing 6 and electrically connected to power source conductor 59. Since slave relay movable contact member 4i) may be in contact with either contact point 41 or 4Z and thus in contact with connecting yconductor 57 or 55, respectively, and silencer switch. 56 'may be in` contact with either conductor 57 or 5S, depending upon the operating state of the system, alarm housing tamper switch 61 is arranged so that any opening of housing 6 will'move the tamper switch movable contact arms into contact with both conductors 57 and 55, thus putting B+ on both these conductors and energizing both alarm indicators independent of the positions of switches 11 and 56.

I desire that it be understood that my test circuit as herein set forth is equally applicable to both types of alarm systems of the classes as set forth in my copending applications Serial Number 671,013, tiled July 10, 1957 for Electronic Barrier, and Serial Number 670,999, tiled July l0, 1957, for Security Alarm System.

While I have described my invention in certain preferred embodiments, I realize that modifications may be made and I desire that it be understood that no limitations upon my invention are intended other than may be imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

il. In a security alarm system, a power source, switching means connected with said power source, an oscillator circuit energized by said power source through said switching means, an antenna system, a circuit enclosing housing connected in said antenna system, an antenna connecting conductor, an antenna tuning circuit connected with said antenna system by said antenna connecting conductor, said antenna system and said circuit enclosing housing radiating an electromagnetic eld, a detection circuit connected with said antenna system, a balanced alarm relay circuit connected with said detection circuit, a normally energized slave relay connected to said balanced alarm relay circuit, an alarm indicator, conductors connecting said alarm indicator with said normally euergized slave relay, a test circuit coil, one end of said coil being open, said coil being disposed about said antenna connecting conductor, a test circuit relay havingl a movable contactor operating with respect to a xed contact, and a series circuit including said contactor connected to the other end of said test-circuit coil and contacting said fixed contact for connectingsaidl coil to ground for simulating-conditions of the approach of an intruder to said antenna system and operating said alarm indicator.

2 In: a-security valarm-system as set forthi in claim l in which said test circuit coil comprises -apluralityA of electrically conductive turns insulated from said antenna connecting conductor and terminating in a free end immediately adjacent said antenna` connecting conductor.

3. In a security alarm system, a circuit enclosing housing, a balanced antenna system, an oscillator circuit, said circuit enclosing housing connected in said balanced antenna system and both radiating an electromagnetic eld when said oscillator circuit is energized, a detection circuit, a balanced alarm relay, a slave relay having a movable contactor and iixed contacts, said detection circuit coupled to said balanced antenna system and arranged to energize said balanced alarm relay, said slave relay connected in the output circuit of said balanced alarm relay and being in the normally energized state, an alarm indicator housing, an alarm indicator, an alarm silencing switch, an alarm indicator power means, said alarm indicator housing enclosing said alarm indicator, said alarm silencing switch and said alarm indicator power means, conductors connecting said movable contactor and said fixed contacts with said alarm indicator power means and said alarm indicator, said alarm silencing switch connected to said alarm indicator and movable between two of said connecting conductors, means coupled to said circuit enclosing housing and connected to said connecting conductors to energize said alarm indicator on the opening of said circuit enclosing housing when said oscillator circuit is deenergized, and means coupled to said alarm indicator housing and connected -to said connecting conductors to energize said alarm indicator on the opening of said alarm indicator housing when said oscillator circuit is energized or deenergized.

`4. In a security alarm system as set forth in claim 3, said means coupled to said alarm indicator housing and connected to said connecting conductors being a doublepole-double-throw tamper switch operable on the opening of said housing.

5. In a security alarm system as set forth in claim 3, the said two connecting conductors between which the alarm silencing switch is movable being the conductors connecting said iixed contacts with said alarm indicator.

6. In a security alarm system as set forth in claim 3, in which said means coupled to said alarm indicator housing and connected to said connecting conductors is a tamper switch disposed in series with said alarm indicator power means and said conductor connected to said movable contactor and movable out of contact with said conductor connected to said movable contactor and into contact with said conductors connected to said iiXed Contact on the opening of said alarm indicator housing.

7. In a security alarm system as set forth in claim 3 in which said means coupled to said circuit enclosing housing and connected to said connecting conductors is a tamper switch disposed in series with said conductor connecting said movable contacter with said alarm indicator power means, being movable into contact with said conductor connecting said iixed contact which is normally energized to said alarm indicator on the opening of said circuit enclosing housing.

References Cited in the iile of this patent UNITED STATES PATENTS

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2390221 *Jul 3, 1943Dec 4, 1945American District Telegraph CoAlarm system
US2615970 *Sep 12, 1951Oct 28, 1952Alertronic Protective Corp OfDummy intruder for intruder detection systems
US2697824 *Jun 26, 1953Dec 21, 1954Petcar Res CorpTest circuit for flame detector systems
US2749537 *Mar 21, 1955Jun 5, 1956Holmes Electric Protective ComDevice for detecting motion in a confined space
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3009137 *Apr 10, 1958Nov 14, 1961Reeve Electrical Co IncVault protection
US3099826 *Jan 2, 1958Jul 30, 1963Westinghouse Electric CorpStatic logic annunciator
US3103003 *Jun 2, 1959Sep 3, 1963Diebold IncCapacity alarm system
US3129415 *Jan 3, 1961Apr 14, 1964Westinghouse Electric CorpProximity detector
US3162848 *Oct 28, 1959Dec 22, 1964Mulvey Louis BElectrical system useful for intrusion alarm with selective sensitivity
US3237179 *Jul 13, 1961Feb 22, 1966Jr John E LindbergHeat detection device with test system
US4024519 *Oct 6, 1975May 17, 1977American District Telegraph CompanyIntrusion alarm test system
U.S. Classification340/502, 340/539.14, 340/515, 340/506, 340/539.1, 340/550
International ClassificationH04B1/04, G08B13/24
Cooperative ClassificationG08B13/2491, H04B1/04
European ClassificationH04B1/04, G08B13/24C