US3005191A

US3005191A - Security alarm system

Info

Publication number: US3005191A
Application number: US670999A
Authority: US
Inventors: Kenneth H Schmidt
Original assignee: MOSLER RES PRODUCTS Inc
Current assignee: MOSLER RES PRODUCTS Inc
Priority date: 1957-07-10
Filing date: 1957-07-10
Publication date: 1961-10-17
Anticipated expiration: 1978-10-17

Description

Oct. 17, 1961 K. H. SCHMIDT 3,005,191

SECURITY ALARM SYSTEM Filed July 1o, 1957 2 Sheets-Sheet 1 lil CE- CoA/mm nv/7' l x u nu manana 1| N N Y \Uumununn iv N t uu L f l Si l I INVENTOR M ae, 505ML,

BY 6K.

ATTORNE Oct. 17, 1961 K. H. SCHMIDT SECURITY ALARM SYSTEM 2 Sheets-Sheet 2 Filed July l0, 1957 3,005,191 SECURITY ALARM SYSTEM Kenneth H. Schmidt, Danbury, Conn., assigner to Mosler Research Products, Inc., Danbury, Conn., a corporation of Delaware Filed .iuly 10, 1957, Ser. No. 670,999

Claims. (Cl. 340-258) My invention relates broadly to electronic security alarm systems, and more particularly to a transistorized, capacity-type alarm system, with an automatic self-supervisory circuit for non-operating periods of the alarm system.

.One of the objects of my invention is to provide a capacity-type alarm system which provides protection and electronic supervision of the connecting lines between system units during non-operating periods of the capacity alarm system.

Another object of my invention is to provide a supervisory circuit for the connecting conductors between system units which is automatically switched into operation when the oscillator and resonant antenna circuits of the capacity-type alarm system are deenergized.

Another object of my invention is to provide a capacity-type alarm system in which the connecting lines between system units are under the constant supervision of an ultra-sensitive alarm producing relay during operating periods of my capacity-type alarm system.

Another object of my invention is to provide a capacity-type alarm system which goes into an alarm condition whenever the system is turned on, to notify the guard at the remote surveillance station that the area is ready to be secured.

Another object of my invention is to provide a capacity-type alarm system which goes into an alarm condition whenever the system is turned off in order to prevent unauthorized deenergizing of the system.

Another object of my invention is to provide a compact, self-powered, transistorized capacity-type alarm system.

A further object of my invention is to provide a capacity alarm system in which the components of the oscillator, antenna tuning, and detector circuits are under constant electronic surveillance in order to prevent any unauthorized tampering with the components of said circuits.

Other and further objects of my invention are set forth more fully in the specification hereinafter following by reference to the accompanying drawings, in which: i

FIG. l is a simplified block diagram in schematic arrangement of my capacitance-type alarm system;

FIG. 2 is a perspective view of a typical installation of the capacity alarm system of my invention and particularly showing the construction of the antenna system and the manner in which a'multiplicity of protected areas may be electronically observed at a remote central station;

FIG. 3 is an overall electrical schematic diagram of the capacity-type alarm system ofmy invention.

My invention is directed to the construction of anrelectronic security alarm system. in which the objects under 'i States Patent O ICC 2 netic field will upset the balance of the relay circuit thus sending in an alarm since the amount of RF energy stored inthe iield has been changed.

The antenna resonating circuit is tuned so that any unauthorized tampering with the connecting lines between system units duringoperating periods will cause a current change in the balanced relay circuit thus throwing the alarm relay and initiating the alarm.

Whenever the system is turned on or oil there is a current change in the balanced relay circuit .of sutlicient magnitude to cause the alarm to be initiated due to the system imbalance thus created.

Y During non-operating periods `of the alarm system, that is, when the oscillator and antenna system circuits are deenergized, an independent supervisory circuit is `automatically switched into the system which by-passes the oscillator, antenna tuning, `and detector circuits and impresses a voltage across the connecting lines between the system units. Any tampering with the connecting line while the system vis in this mode of operation will change the current `to the balanced alarm relay circuit and cause an ammeter installed in that circuit to indicate an unbalanced condition. 'I hus the connecting lines `between the units of the system are under protective sur` veillance during both operating and non-operating periods of the antenna system. This is also true of the oscillator, antenna tuning, and detector circuits since the housing in which `they ,are encased is associated with a tamper switch which is in series with one of the connecting lines.

In referring `to the drawings in more detail, similar numerals refer .to similar components throughout this specification.

In FIG. A 1 I have shown the basic block diagram of my capacity alarm system. ',It consists of: control unit 1; guard `unit 2; and the objects, assembly, or area `to be protected designated by reference character `It. Reference Acharacter 4 designates the antenna connection line connecting the control unit 1 to the insulated object or area under protection which forms the antenna system,

, .by transmitting radio'rrequency energy from control unit protection are connected in series and form an antenna 'balanced for the particular antenna system and the prence of any additional body or object inthe electromag- 2a into an antenna system, comprised in this particular illustration, of conductor 4a; tile cabinets 7, 8 and 9; and .safe 10. The cabinets and safe are insulated from ground .by insulating blocks 11and wired together at 12, 13, and 14 with heavy braid to complete the antenna circuit betweenthe objects. The system is `balanced for the particularsafe and .file cabinets or other objects or area under protection. ,Any additional object, such as a human being, .placed ,in the sensitve area which entirely surrounds .the safe, will change the amount .of radio frequency energy stored in the field. This in turn will cause unbalance vin `the alarm unit 2a, which is: the guard unit .for zone A. i

This capacitance systemmay-be either a single system installation or a multiple system installation as .shown in EHS. 2. .Here i hare .shown the guard units 2a, 2b, v2c and 2d of four separate systems installed at a common central station lto enable one guard to maintain electronic surveillance over four separate removed areas.` With thisyarrangernentkan intrusion in .one of the protected V3 Y areas will indicate an alarm at its associated central station guard unit, thus pin-pointing the area of intrusion so the guard knows exactly where to take immediate action. The systems are not associated in any manner except that they may .usel a common guard unit` power Source.

I have shown the electrical wire schematic diagram of my invention in FIG. 3. The diagram is divided into two y.basic sections, the control unit 1 and the guard unit 2.

The control unit is self-powered by one 1.5 volt dry cell type battery 15 which supplies-B'- voltage for said unit. Because a transistor is utilized in the circuit rather than a vacuum tube, this one battery will operate the system for approximately one year. The Day-Night switch 16 -`is connected in series with the power supply conductor With switch 16 in the Night position, B- through conductor 22, after being filtered by bypassca'pacitor -23, is suppressed on the transistor oscillator circuit which 7, 8, and 9, and safe 10 in FIG. 2). 'I'he antenna system is tuned or resonated by selecting the appropriate i tap on the primary of transformer 29 and adjusting tuning capacitor 28 while observing tuning meter 30 as an indicating means for such procedure. The circuit isk tuned so that there is a small voltage across the secondary winding of detector transformer 29. The sensitivity of the antenna system can be increased by changing the value of or removing desensitizing capacitor 27.

`The detection circuit is comprised of the secondary winding of transformer 29; blocking capacitor 31; a rectitier circuit consisting of crystal' dioder 32 connected to ground and crystal diode 33 connected in series with Vthe detector output conductor 34; and by-pass capacitor' 3S 'to ground o'n the output of diode 33. The remainder of the control unit circuit consists of tuning meter 30 which is a micro-ampere meter, and .tamper switch 36 connected in vseries with output conductor 34. Tamper switch 36 is positioned in the control unit in such a manner that it completes the control unit output circuit when the lcontrol unit housing lis in place while thesame circuit is opened when the control unit housing is'removed.

This is to prevent unauthorized tamperingwith the control unit componentsV as will be discussed later. Ground line 6 in the control unit is grounded at the control unit.

Control

unit output lines

34 and 6 arev connected to

conductors

37 and 6", respectively, in guard unit 2 by connecting lines and 6, respectively. Protection meter 38 is connected in series with conductor 37 and is 'a duplicate to tuning meter 30. This meter is placed-in the guard unit so a guard at a remote location' is assured that everything is in proper balance at the protected area, and no connecting lines, etc.,V have been tampered with. If one of the tile cabinets, etc., had become disconnected or grounded during the Day period, the meter would not read in the safe portion of the meter scale when

switch

1,6 is switched to the Night position. If the control unit housing or the connecting lines 5 and 6 were tampered with while switch 16 is in the Day position the -meter would read in the unsafeportion of the scale but no change in meter indication will result from-tampering with the antenna system components while this switch is in the Day position. v

When switch 16 is switched to the Day position,'B- excitation is removed from the oscillator, circuit which .results in deenergizing the antenna system and the detector circuit. B- is now applied to a supervisory circuit vcontrol unit output current. manual reset alarm relay responds to any change in curwhich provides for the protection and supervision of the control unit housing and the connecting lines during the non-operating or Day periods of the alarm system. This supervisory circuit is comprised of switch 16 in the Day position, voltage drop resistor 50 andrDay balance resistor 51, all in series with conductor 52 which connects to detector .output conductor 34 between the junction of crystal diode 33 and by-pass capacitor 35, and tuning meter 30, thus inserting the supervisory circuit in series with tuning meter 30.

The principal portion of the guard unit circuit consists of the balanced alarm relay circuit which is composed of compensation capacitor 39 in series with ultrasensitive alarm relay coil 40 shunted by load resistor 411 and also b y by-pass capacitor 42. Movable contact arm 43 of the manual reset alarm relay is grounded. The alarm relay stationary contacts `44 are connected to one end of slave relay coil 45 while the other end is connected to B+. Movable contact arm 46 of the slave relay is `connected to Bi-i- Two alarm signals connected in parallel are provided at the guard unit, a buzzer 47 and a light 48. When the system becomes unbalanced and goes into alarm both alarm signals will indi- .cate since slave Arelay contact control arm 46 impresses Bi-lacross each. The buzzer can be silenced by means of silencer switch 49 but the light will not go out until .the system is rebalanced and operating properly. To

prevent the guard from foregetting to turn the buzzer back on, the silencer switch must be returned to the normal operating position` when the unit is rebalanced or the buzzer alarm will indicate since in this state the slave relay contact arm 46 when it returns to its deenergized position impresses Bi-lacross the buzzer if the silencer switch has not been returned to its normal operating position. l

The light and buzzer indicators in the guard unit may .operate lfrom volts A.C. power with a 6 volt standby battery so arranged thatif the A.C. power supply vshould fail, all components of the guard unit would continue to operate without interrupt-ion since the stand-by `battery supply would be switched into the circuit auto- .matically. With switch 16 in the Night position a wouldbe intruder passing into or through the particulararea under protection will change the amount of radio frequency energy stored in the field by the antenna system, since the system is balanced for the particular area under protection. This changes the capacity of the antenna system and results in a change in voltage across the secondary winding of transformer 29 and thus a change in The ultra-sensitive guard rent exceeding two micro-amperes, thus the above current vchange activates the alarm relay coil 40 which results in coil 45 of the slave relay being activated and impressing B+. across the alarm indicators by means of slave relay movable contact 46.

Since there is always a small voltage present across the secondary winding of transformer 29, if an unauthorized person opened the` control-unit housing the tamper switch 36 would break the output circuit, causing the 'current to drop to zero and this current changewould throw the alarm relay, and through the chain reaction set forth above, the alarm would be activated.

' The alarm will also be activated if the connecting lines between, the control unit and the guard unit are cut, jumpered, or if the wire is bared and touched with the linger or a metal object, because each changes the current in the circuit sufficiently to instantly activate the Aalarm relay.

I When the Day-Night switch is switched from Night to Day the oscillator is deenergized; thus the voltage across the secondary of transformer 29 disappears'so the alarm is activated from the resulting eurent change or disap pearancegTrhis eliminates the possibilityV of an intruden turning .off the alarm system since such a move sets of@ the alarm. When it comes time to operate the system in the Day position the switching-over process will activate the alarm and the guard athis remote location being notified that it is an authorized system switch-over can manually reset the alarm relay thus deenergizing the alarms.

During Day position operation a B- D C. Voltage is impressed across the connecting lines 5 and 6 and any cutting or breaking of such lines or any opening of the control unit housing will result in the meters ceasing to indicate since they are in series with the tamper switch and connecting lines. No alarm is activated in this state since compensation capacitor 39 blocks the DC. voltage and thus makes the alarm relay coil 40 insensitive to D C. current changes.

Since during Day operation the antenna system (i.e. safe, file cabinets, etc.) is not under protection the objects or area of the antenna system may be touched and used as they customarily are during the day. Any damage to this section of the system during Day operation will not be discovered until the system is switched to Night operation.`

When switch 16 in the control unit, which is located in the area under protection, is switched to the Night position thecorresponding guard unit goes into alarm because of the current change from zero to some value. This notities the guard at the guard unit that the control unit has been switched into Night operation. If during Day operation someone had purposely or accidentally damaged the system, such as breaking or cutting an antenna connection, grounding, or any break-down of internal components of the control unit, meters Sti and 38 would indicate in the danger zone, indicating a system unbalance. This would put the guard on notice of a failure in the system which must be corrected by troubleshooting If the guard unit meter indicates in the balanced zone, the guard at the guard unit secures the area by resetting the 'manual reset alarm relay, stopping the alarm and thus putting the system in operation until such time as the sensitive balance is upset by some cause. No warning signal is audible or visible in the secure area so that the ywould-be intruder setting olf the alarm does not know he has informed the guard of his presence.

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

l. An alarm system comprising a control unit disposed in the area to be protected, a guard unit disposed in an area remote from the protected area, and two connecting lines electrically interconnecting said guard unit and said control unit, said control unit comprising a direct current power Source, an oscillator circuit, a manually operated switch having first and second operative positions, said switch when in said rst position being effective to interconnect said power source and said oscillator circuit, an antenna system connected to said oscillator circuit, an antenna tuning circuit connected with said antenna system, a detection circuit interconnected with said antenna system, the output leads of said detection circuit being interconnected to said con necting lines, a bypass line effective to interconnect said switch with one of said connecting lines when said switch is in said second operative position, whereby when said switch is in said first position said oscillator, said antenna system and said detection circuit are energized and apply an alternating current signal to said connecting lines, said signal being modified upon any intrusion into the protected area, and whereby when said switch is in said second position said oscillator is deenergized and a direct current signal is applied from said power source across said connecting lines which signal provides means at the guard unit for supervising saidV connecting lines, said guard unit comprising an ultra sensitive balanced arm relay circuit energized from said connecting lines, an alarm indicator energized in response to the actuation of said balanced arm relay, and indicating means responsive to current flow through said connecting lines.

2. An alarm system comprising a control unit disposed in the area to be protected, a guard unit disposed in an area remote from the protected area, and two connecting lines electrically interconnecting said guard unit and said control unit, said control unit comprising a direct current power source, an oscillator circuit, a manually operated switch having first and second operative positions, said switch when in said f rst position being effective to interconnect said power source and said oscillator circuit, an antenna system connected to said oscillator circuit, an antenna tuning circuit connected with said antenna system, a detection circuit interconnected with said antenna system, the output leads of said detection circuit being interconnected to said connecting lines, a bypass line eective to interconnect said switch with one of said connecting` lines when said switch is in said second operative position, whereby when said switch is in said first position said oscillator, said antenna system and said detection circuit are energized and apply an alternating current signal to said connecting lines, said signal being modiiied upon any intrusion into the protected area, and whereby when said switch is in said second position said oscillator is deenergized and a direct current signal is applied from said power source across said connecting lines which signal provides means at the guard unit for supervising said connecting lines, said guard unit comprising an ultra sensitive balanced arm relay circuit energized from said connecting lines, an alarm indicator energized in response to the actuation of said balanced arm relay, and indicating means responsive to current iiow through said connecting lines, the current change occurring upon shifting of said switch from one position to another being of sui'licient magnitude to actuate said balanced arm relay.

3. An alarm system comprising a control unit disposed iu the area to be protected, a guard unit disposed in an area remote from the protectedv area, and two connecting lines electrically interconnecting said guard unit and said control unit, said control unit comprising a direct current power source, an oscillator circuit, a man ually operated switch having first and second operative positions, said switch when in said rst position being effective to interconnect said power source and said oscillator circuit, an antenna system connected to said oscillator circuit, an antenna tuning circuit connected with said antenna system, a detection circuit interconnected with said antenna system, the output leads of said detection circuit being interconnected to said connecting lines, a bypass line eiective to interconnect said switch with one of said connecting lines when Vsaid switch is in said second operative position, whereby when said switch is in said first position said oscillator, said tenna system and said detection circuit are energized and apply an alternating current signal to said connecting lines, said signal being modified upon any intrusion into the protected area, and whereby when said switch is in said second position said oscillator is deenergized and a direct current signal is applied from said power source across said connecting lines which signal provides means at the guard unit for supervising said connecting lines, said guard unit comprising an ultra sensitive balanced arm relay circuit energized from said connecting lines, an alarm indicator energized in response to the action of said balanced arm relay, and indicating means responsive to current iiow through said connecting lines, said last named means comprising a meter, a resistance in said bypass line edective to limit the current flow through said line to the same order of magnitude as the normal current output of said detector, whereby said meter is effective to provide a current reading with said switch in either said first or second positions.

r4. An alarm system comprising a control unit disposed in the area to be protected, a guard unit disposed in an area remote from the protected area, and two connecting lines electrically interconnecting said guard unit and said control unit, said control unit comprising a housing enclosing a direct current power source, an oscillator circuit, a manually operated switch having first and second operative positions, said switch when in said Iiirst position being eifective to interconnect said power source and Vsaid oscil-lator circuit, an antenna system connected to lsaid oscillator circuit, an antenna tuning circuit connected with said antenna system, a detection circuit interconnected with said antenna system, the output leads of said detection circuit being interconnected to said connecting lines, a normally closed tamper switch mounted within said housing, said switch having con* tacts in one of said output lines and being adapted to open upon opening of said housing, `a bypass line effective to interconnect said switch with one of said connecting lines when said switch is in said second operative position, whereby when said switch is in said iirst position said oscillator, said antenna system and said detection circuit are energized and apply an alternating current signal to said connecting lines, said signal being modiiied upon any intrusion into the protected area, and whereby when said switch is in said second position said oscillator is deenergized and a direct current signal is applied from `said power source across said connecting lines which signal provides means at the guard unit for supervising said connecting lines, said guard unit comprising an ultrasensitive balanced ann relay circuit energized from said connecting lines, an alarm indicator energized in response to the actuation of said balanced arm relay, and indicating means responsive to current ow through said connecting lines.

5. An alarm system comprising a control unit disposed in the area to be protected, a guard unit disposed in an area remote from the protected area, and two connecting lines electrically interconnecting said guard unit and said control unit, said control unit comprising a direct current power source, an oscillator circuit, a manually operated switch having iirst land second operative positions, said switch when in said rst position being effective to interconnect said power source and said oscillator circuit, an antenna system connected to said oscillator circuit, an antenna tuning circuit connected with said antenna system, a detection circuit interconnected with said antenna system, the output Aleads of said detection circuit being interconnected to said connecting lines, a meter in one of said output leads, a bypass line 'effective to interconnect said switch with one or said connecting lines when said switch is in said second operative position, whereby when said switch is in said iii-st position said oscillator, said antenna system and said detection circuit are energized and apply an alternating current signal to said connecting lines, said signal being modied upon any intrusion into the protected area, and whereby when said switch is in said second position said oscillator is deenergized and a direct current signal is applied trom said power source across said connecting lines which signal provides means at the guard unit for supervising said connecting lines, said guard unit comprising an ultrasensitive balanced arm relay circuit energized from said connecting lines, an alarm indicator energized in response to the actuation of said balanced arm relay, and a Ymeter responsive to current iiow through said indicators.

References Cited in the tile of this patent UNTEDSTATES PATENTS Muehter J-uly 5, 1960