US3634844A

US3634844A - Tamperproof alarm construction

Info

Publication number: US3634844A
Application number: US837195A
Authority: US
Inventors: John G King
Original assignee: JOHN G KING
Current assignee: JOHN G KING
Priority date: 1969-06-27
Filing date: 1969-06-27
Publication date: 1972-01-11
Anticipated expiration: 1989-01-11

Abstract

A vibration responsive transducer, in the form of an alwaysclosed leaf contact switch, provides a variable resistor for triggering a latching switch to enable an alarm device. If the transducer is predetected, an attempt to short circuit or open circuit it will also trigger the latching switch by way of a shunt path leading from the transducer. In addition to the transducer per se and the above-mentioned alarm arrangement, a complete tamperproof automobile alarm construction is provided and includes: enable delay, alarm timing, reset, and amplifier circuitry coupled between the transducer, the latching switch and the alarm device. The alarm device is also coupled to be enabled by the circuit closing of the electric system of the automobile.

Description

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[72] Inventor John G.King 3,l72,0l6 3/l965 Kenlinc BBB/99X 801 South 11th Street, Maywood, lll. 3,286,250 I III 966 Teitelbaum 340/276 60153 3,422,398 [/1969 Rubin 340/63 [2|] Appl. No. 837,195 3,466,643 9/l969 Moorefield 340/276 X [22] Filed June 27,1969 3,52l,26 6 7/l970 Hall 340/261 [45] Patented 197.2 Primary Examiner-John W. Caldwell Assistant Examiner Michael Slobasky [54] TAMPERPROOF ALARM CONSTRUCTION 21 Claims, 3 Drawing Figs.

[521 US. Cl 340/261, STRACT: A ibrat n re pon transducer. in the orm 7 340/276, 338/92 Of an always-closed leaf contact switch, provides a variable re- [51 Int. Cl .,G08b 13/12 l l' f r triggering a latching switch to enable an alarm [50] Field of Search 340/261, device. If the transducer is predetected, an attempt to short 258, 276, 63, 65; 338/43, 47, 99, 104, I 13; Circuit or open circuit it will also trigger the latching switch by ZOO/61.48, 166 H way ofa shunt path leading from the transducer.

in addition to the transducer per se and the above-menl l Relerences Cited tioned alarm arrangement, a complete tamperproof automo- UNITED STATES PATENTS bile alarm construction is provided and includes: enable delay, 3 158,850 11/1964 Poznanski 340/261 x alarm "mine and circuitry Coupled between 539 3/1929 Rubenm 338/99 the transducer, the latching switch and the alarm device. The 2'974'52l 3/1961 phdpsn 200/6148 X alarm device is also coupled to be enabled by the circuit clos- 31351951 6/1964 Byrne 340/258 x 8 electric system mommie- )1. FY? Q 5 8 $6 2 6Chi 54 I 1 y ALARM ROOM mama) m1 1 ma 5 3 4 28/ will/177111011 V 22 I2 34 \4 ALARM Inventor JOHN 6. KING BY 5 Z Z 9 y ATTYS.

TAMPERPROOF ALARM CONSTRUCTION BACKGROUND OF THE INVENTION This invention concerns electronically operated alarm systems for the prevention of illicit entry into protected environments, detection of the movement of protected articles, and specifically for generating an alarm whenever a protective transducer is subject to vibrations due to illicit activities.

The history of alarm apparatus and the forms of such apparatus for preventing theft and other illicit activitiesrelative to property and goods is as long and multiformed as the history and facets of thievery and related activities.

One small, but increasingly important, form of detecting and alann apparatus is that which responds to'vibration of the protected site. For example, the opening of a window or door by a burglar will induce vibrations in the window or door and adjacent framework. The breaking of a window, opening of the hood or trunk of an auto, movement of a television set from a motel, etc., all will produce vibrations in and around the item being handled for illicit purposes. Such vibrations are subject to detection and have been used to trigger alarm apparatus.

One such prior detector operates upon the pendulum principle and can be produced cheaply. Often, such transducer lacks sensitivity and is of such relative size as to be easily discovered and avoided or dismantled by a burglar.

Pressure responsive transducers have been considered for vibration detectors; however, the initial cost of manufacturing such units and their sensitivity to atmospheric conditions have presented commercial drawbacks.

SUMMARY OF THE INVENTION Notwithstanding the above, a vibration responsive transducer, if compact, inexpensive, durable, and s'ensitive,. would be highly desired as a basic component in a tamperproof alarm construction-such is a primary object of this invention.

Another object of this invention is to provide an improved electronic alarm construction having a vibration responsive transducer.

A further object of this invention is to provide an especially sensitive alarm construction which responds to vibrations, attempts to open circuit the vibration transducer, as well as attempts to short circuit its vibration transducer.

To achieve the above and other objects, the invention provides a vibration responsive transducer which acts as a variable resistor for connection to electronic alarm circuitry, par ticularly for connection to the control input of a latching switch. Such transducer and switch in combination with amplifying, delaying, protective shunting and alarm means form an especially effective and tamperproof alarm construction.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a sectional side elevation of the vibration transducer of this invention;

FIG. 2 is an electrical schematic of a simple alarm construction employing the subject vibration transducer and a protective shunting circuit; and v FIG. 3 is an electrical schematic of an alarm construction primarily incorporating the schematic of FIG. 2 and augmenting it for use in the protection of an automobile.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. I, the subject vibration transducer is shown in enlarged scale. luzg n ipgse s a long r arrow hgusing 12, of plastic or other like substance, preferably of electrically insulating material. Such housing can be easily attached to a surface which would vibrate when violated by illicitactivityfFor convenience, the housing can be provided with a passageway 14 through which a fastener-screw, nail, etc.,-can pass so as to hold the length of the transducer against the surface which is to be subject to vibration.

The interior of the housing 12 defines a cavity I6 for holding in relative position the transducing element 18 per se. Such transducing element 18 is readily recognizable as primarily comprising a simple contact switch having a pair of

leaf springs

20 and 22 having end portions mounted through and spaced apart by an insulating member 24 so as to provide

electrical terminals

26 and 28, respectively, external the hous' ing 12. The opposite end of the leaf 20 carries a contact point 30; whereas. the facing portion of the leaf 22 carries a contact pad 32.

Completing the transducing element is a setscrew 34 which threads through the housing 12 for applying variable mechanical bias to the leaf 22, while always maintaining the contact point and pad in electrical conducting relationship. The reason for such arrangement will become clear from the subsequent description. Depending upon the position of the setscrew, the transducing element will be less or more sensitive to vibrations, increased bias decreasing the sensitivity.

Although the leaves and their contacts are biased together, vertically, as shown in FIG. 1, they are relatively free to move in sympathy with and because of the vibrations of the surface to which the transducer is secured. As a result, and depending upon the frequency and intensity of the vibrations, the contact point 30 will move relative to the contact pad 32, i.e., on its surface, while maintaining electrical surface-to-surface contact.

Experimentation has indicated that the lengths of the leaves control the vibration frequencies to which the transducer is more responsive. Hence, the transducer can be manufactured so as to be tuned to a specific range of vibrations and thereby.

be employed as a detector of specific vibrations, as well as relatively insensitive to other vibrations. Thus designed, the transducer is adapted for uses remote from theft alarms and could conceivably be employed in scientific and industrial instrumentations as a highly precise, yet compact and rugged detector of specific vibrations.

Returning to the fact that the transducing element is basi' cally an electrical switch, the vibration-induced relative movement of the contact point 30 and pad 32 has been found to effect changes in the series electrical resistance measured from the terminal 26 to the terminal 28. By use of a pad 32 which is imperfect, because of impurities, and/or an uneven contact surface, the magnitude of the resistive changes is increased. Accordingly, a low-quality switch is preferred over one of high quality, for providing a more responsive vibration transducer. Such changes in resistance have been found adequate to trigger devices such as transistors and silicon-controlled rectifier latching switches, as will be discussed next with reference to FIG. 2.

In the schematic of FIG. 2, the reference number 10 is directed to transducer means illustrated as a variable resistor, since such is the electrical equivalent of the transducer 10. In a practical security protection use, several of the transducers could be serially connected and define the transducer means 10. For example, in the protection of an apartment, a transducer could be-secured to each entrance door and to each window frame area. I

Leading from the

terminals

26 and 28 are shielded

conductors

36 and 38. A resistor 40 is coupled to the shielded portion of the

conductors

36 and 38 and is connected by lines 42 and 44 to the positive side of an energy source 46, which can be a low-voltage battery. A resistor 48 is connected between the line 44 and the central portion of the conductor 38. As later to be discussed, the resistors 40 and 48 will be in parallel if the shield and central portion of the

conductor

36 or 38 are shorted together.

An alarm device 52 has one side also connected to the positive side of the battery 46 and the line 44, and its other side is coupled to the negative side of the battery through an SCR latching switch 54, a connecting line 56, and an enabling switch 58. The gate lead 60 of the SCR is connected to the central portion of the conductor 38; whereas, a resistor 62 is connected between the central portion of the conductor 36 and the connecting line 56. In this manner, the resistor 62 is in series with the transducer means and would be in series circuit with the parallel connection of the transducer and the resistor 40 if the shielding of the

conductor

36 or 38 were shorted to its central portion. 3

As well known, the SCR is a switching device which will conduct from anode to cathode when triggered by a suitable bias, normally by a positive current to the gate lead 60. Once conducting, this device will remain latched even in the absence of a continuation of the initiating gate lead bias, and requires shutoff deenergization to stop its operation. Of special merit is the fact'that the triggering signal on the gate lead can be very small and of very short duration.

In the operation of the FIG. 2 embodiment, and in the quiescent condition, the enabling switch 58 is closed and system parameters are chosen so that the SCR 54 is nonconducting, but the gate to cathode and the anode to cathode relationships are such that a slight change in the gate bias will trigger the conduction of the SCR. The alarm device 52 is not enabled in the quiescent condition, since the SCR acts as an open circuit to the energy source 46. In the event of an alarmcondition vibration of the transducer means 10, it leaves and contacts will be set into motion to elicit a change in resistance that is coupled by the conductor 38 to gate lead 60 as a triggering current signal, which sets the SCR into conduction. Such conduction provides a complete circuit for the alarm device, which operates in its alarm mode.

Even if the vibration is only momentary, the alarm device will remain enabled until the enabling switch 58 is opened or the battery 46 taken out of circuit, as by opening of the line 44 or'56. Obviously, the alarm device 52, the switch 58 and the battery source 46 should be located remote from the transducer means 10, so that a burglar cannot disable the system either before or immediately after the alarm is triggered.

-' interrelated third circuit path for triggering the SCR. Assuming that the transducer means and its shielded conductors are seen'and accessible, such as through a partly open window,

that was opened prior to the closing of the enabling switch 58,

a burglar might attempt to disconnect the transducer by cutting one of the

conductors

36 or 38. Such cutting act, especially if it is attempted with a knife, pliers or other electrically conductive tool, could cause the shield and the central portion of the conductor to be short circuited together and place the resistor 40 in shunt, as previously described, to effect a resistive change to induce the triggering of the SCR.

Even if the burglar was able to cut through the conductor 36 and/or 38 or otherwise fully remove the transducer from the circuit without causing a vibration triggering or a short circuit triggering of the SCR, the resistive relationships of the remaining elements, the variable resistor 10 being out of circuit, would then induce a triggering of the SCR. Hence, the alarm construction is effectively tamperproof.

FIG. 3 presents an alarm construction specifically designed for protection of an automobile or truck; however, those interested in the protection of other forms of property, will find disclosed herein circuitry, subcombinations and combinations of tamperproof protective alarm construction adaptable for many needs.

Once again, the vibration-sensitive transducer means 10 is shown as a variable resistor, and comprises one or more of the transducing elements electrically in series between ground and the positive side of the source 46. Typically, the transducers could be secured to the doors or door frames, window areas, hood, trunk, etc.

Also present, as in FIG. 2, is the alarm device 52, the SCR latching switch 54, and the enabling switch 58. The latter purposely is shown connected in series between the cathode of the SCR and the positive side of the source 46 to emphasize that the different configuration in FIG. 2 is not limiting.

Nevertheless, the basic vibration triggering, due to an induced resistive change that triggers the SCR via its gate, still is present.

As a practical matter, the driver of the protected automobile, after leaving and locking the driver's side door, could close the switch 58 by' a form of key-closed switch portion mounted to the outside of the automobile or, and as desirably provided in FIG. 3, he would close the switch 58 before leav- 'ing and locking the automobile, and then leave and lock it.

The latter procedure adds another safeguard, that of the absence of any externally available part of this tamperproof alarm construction.

'Of course, the closing of the switch 58 before the doors are last opened and closed by the exiting driver and passengers, would trigger the alarm device 52, were it not for a special time-delay network. Such network comprises a door-controlled switch 64, mounted to be closed by the closing of that door, having one side connected to the inner conductive portion of the conductor 36, and the other side connected to the shield of the conductor. An RC timing circuit, having a variable capacitor 66 and a resistor 68, is couple between ground, the shield of the conductor 36 and the collector of a transistor 70. The latter has its base connected to the inner portion of the conductor 36 and its emitter connected to the gate lead 60 of the SCR 54. A transducer sensitivity controlling variable re sistor 72 couples the transducer means to the conductor 36.

The operation of the delay network is as follows: after closing the enabling switch 58, the driver closes his door to close the switch 64 and complete circuit paths from the positive side of the source 46 through the

elements

72 and 10 to ground. After a suitable delay of about one-half minute, depending upon'the parameter values of the RC circuit, which would be enough to permit the doorclosing vibrations and other vibrations to subside, the transistor becomes biased so that a subsequent vibration-induced, transducer-changed, base drive will trigger the transistor into conduction and thus trigger the SCR.

The anode of the SCR is connected to a diode 74, which leads to a pair of timing circuits comprising a capacitor 76, a

resistor 78, a resistor and a capacitor 82. Such combination I provides input control potential to an input 84 of an amplifier 85, preferably of the Darlington type. The source 46 and a resistor-86 provide amplifier bias potential. The output of the amplifier is coupled to a grounded relay coil 88 linked to a grounded annature 90. The armature normally abuts a contact 92 coupled to the anode of the SCR by an anode load 'resistor 94. Thus, the anode would be without any load and thereby the SCR forced to turn off as soon as the armature 90 is pulled from the contact 92. When the armature is returned to its normal position, the SCR is again in condition to be enabled.

A contact 96 lies adjacent the armature 90 and is connected to the alarm 52. The positive terminal of the source 46 is also connected to the alarm. Hence, triggering of the SCR will drive the input 84 of the amplifier 85 and energize the coil 88 to pull the grounded armature 90 against the contact 96, thereby completing a circuit through the alarm device to activate it. The RC elements 80 and 82 delay the enabling of the amplifier 85 sufficiently for the relatively large capacitor 76 to fully charge. Thereafter, the amplifier will remain operating until its two RC circuits have timed out. A period of about 2 minutes should be sufficient to discourage an illicit intruder and attract attention to the area. A longer alarm period could be provided, but a continuing alarm is considered undesirable to most installations, since it would become an annoyance to neighboring residents. At the beginning of such operating period, as above discussed, the armature 90 is pulled away from the contact 92 to remove the load 94 from the anode of the SCR; thus, at the end of the alarm period, the coil 88 is deenergized and the armature returns to its normal position to vibration.

Under most conditions, the source 46 would be provided by the battery of the automobile, hence, one of the transducers would be connected to the hood of the automobile so as to respond to any illicit entry to the battery, motor etc.

Supplementary protection can easily be incorporated into the construction shown in FIG. 3 by coupling a switch 98 and a simple amplifier 100 between ground and the alarm device 52. Such switch 93 could comprise a plurality of series-coupled switches indicative of a closed electric circuit; for example, connected to the ignition system, in circuit with the headlights, domelight, taillights, etc. Hence,'any absence or failure of the vibration-induced alarm condition would be supplemented by a closed-circuit detector of illicit use of the automobile.

Accordingly, there has been described a specific form of a resistance-varying, vibration responsive transducer; and a pair of tamperproof alarm constructions for its use. Other uses and modifications of the disclosed constructions is expected to be within the skill of the art without departing from the scope of the invention.

What is sought to be protected by United States Letters Patent is: p

l. A tamperproof alarm construction comprising: vibration responsive electrical transducer means which has one pair of electrically conductive contact members having contact surfaces mechanically biased in a direction normal to said contact surfaces and thereby held into continuous electrical contact, one of said contact members being of leaf spring construc' tion with its said contact surface being movable with respect to the contact surface of the other contact member in a direction normal to the applied bias when subject to environmental vibration, which vibration is applied directly to at least said one contact member, while said contact surfaces continue in electrical and mechanical surface to surface contact,

each said contact member providing an electrical terminal for connection to terminals of the alarm construction, and

said contact members defining, in a quiescent condition, a

first series of electrical resistance with said terminals and, when subject to direct application of vibration, defining at least a significantly different second electrical series resistance with said terminals, the significantly different values of said first and second series resistances being defined by two different locations of the two contact sun faces relative to one another and independent of contact pressure changes therebetween, if any; a latching switch coupled to be responsive to changes in the resistance of said transducer means and to be triggered as a result of the occurrence of said second resistance; and alarm-producing means coupled to said latching switch and enabled thereby when said latching switch is triggered.

2. An alarm construction according to claim 1 in which there is provided,

ariable bias control means disposed relative to at least one of said contact members for adjusting the bias of said contact members.

3. An alarm construction according to claim 1 wherein: at least one of said contact members includes a portion that is irregular in the sense that, at discrete different points thereon, different series resistances can be measured with respect to that contact member.

4. An alarm construction according to claim 1 wherein said latching switch has a trigger input coupled to said transducer means, and

an enabling switch is arranged in series with another input of said latching switch and said alarm means, to provide electrical energy thereto as well as to said transducer means.

5. An alarm construction according to claim 1 in which conduction means having first and second conductor portions, normally electrically separated, connects said transducer means within said alarm construction by way of said first conductor portion, and

resistive means is coupled to said second conductor portion and defines a shunt path with said transducer means in the event of a short circuiting of said conductor portions,

wherebysaid latching switch will be triggered.

6. An alarm construction according to claim 5 wherein said construction means comprises:

a shielded conductor of which the inner conductor is said first conductor portion, and the shield is said second conductor portion.

7. An alarm construction according to claim 5 wherein said transducer means, said resistive means, and said conduction means are interconnected such that open circuiting of said conduction means removes said transducer means from being in circuit with said latching switch, whereby said latching switch will be triggered.

8. An alarm construction according to claim I which further comprises: i

relay means normally positioned to permit said latching switch to be triggered, but when energized, completing a circuit path to an input of said alarm means to enable the latter, while forcing the latching switch to turn off.

9. An alarm construction according to claim 1 wherein closed circuit responsive switching means is coupled to said alarm means to enable same in the event of an alarm circumstance designated by a closed electric circuit condition.

10. An alarm construction according to claim 1 wherein alarm timing means are coupled to said latching switch and said alarm means to hold said alarm means enabled a it predetermined timed after the triggering of said latching switch. in

11. An alarm construction according to claim 10 in which said timing means includes a first RC circuit providing an output to an amplifier.

12. An alarm construction according to claim 15 wherein said amplifier is of the Darlington type, and

a second RC circuit is coupled between said first RC circuit and said amplifier to insure that said firstRC circuit is fully charged before said amplifier is enabled. 13. An alarm construction according to claim ll wherein said alarm timing means further comprises:

relay means normally positioned to permit said latching switch to be triggered, but when energized, coupled between the output; of said amplifier and an input of said alarm means to enable the latter, while forcing said latching switch to be turned off.

14. An alarm construction according to claim 1 wherein latching switch delay enabling means are coupled between said transducer means and said latching switch.

15. An alarm construction according to claim 14 wherein: said latching switch delay enabling means comprises conducting means having first and second conducting portions, normally electrically separated, said first conducting portion coupling said transducer means to said latching switch, an enabling switch for connecting said first and second con-' necting portions, and

a delay circuit coupling said second conducting portion to said latching switch. 16. An alarm construction according to claim 15 wherein said delay circuit comprises: 5 a switching element having its output coupled to said latching switch, said switching element having one input coupled to said first conducting portion, and a delay network coupled between said second conducting portion and another input of said switching element.

17. An alarm construction according to claim 16 wherein said conducting means comprises:

a shielded conductor of which the inner conductor is said first conducting portion, and the shield is said second conducting portion.

18. A vibration responsive electrical transducer for use in the two contact surfaces relative to one another and indevibration detection apparatus such as tamperproof alarm conpendent of contact pressure changes therebetween, if structions which include a pair of electrical terminals for conan nection to said transducer, said transducer comprising: 19 A transducer according 10 l i 18 i hi h there i one of said contact members being of leaf spring construcid d;

with its Said surface being movable with variable bias control means disposed relative to at least one respect to the Contact Surface of the other Contact of said contact members for adjusting the bias of said conmember in a direction nonnal to the applied bias when tact members subject to environmental vibration, which vibration is ap- 20 A transducer according to daim 13 wherein; p i directly at least Said one member at least one of said contact members includes a portion that said contact surfaces continue in electrical and mechaniis irregular in the sense hat at discrete different points cal surface to surface contact, each said contact member providing an electrical terminal for connection to the terminals of the alarm construction, and 15 said contact members defining, in a quiescent condition, a first series electrical resistance with said terminals and, when subject to direct application of vibration, defining at least a significantly different second electrical series resistance with said terminals, the significantly different values of said first and second series resistances being defined by two different locations of thereon, different series resistances can be measured with respect to that contact member.

21. A transducer according to claim l8 which further comprises:

an electrically insulating housing constructed to be flush mounted to the surface of a vibration-monitored area, and

said transducer is constructed and arranged to be especially compact.

CEsisbnrormastsON ZatentNo. 3,634,844 m January 11, 1972 Inventofls) H G KING It is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

zolumn 6, line 32, change "timed! to time--, line 37, change "15" to ellcolumn 7, between lines '4 and 5 insert ---one pair of electrically conductive contact members having contact surfaces mechanically biased in a direction normal to said contact surfaces and thereby held M continuous electrical contact,--.

"si ned and sealed this 22nd day of August 1972.

(SEAL) Atftest: EDWARD M.FLETCHER,JR. RdBERT GOTTSCHALK Attesting Officer Commissioner of Patents

Claims

1. A tamperproof alarm construction comprising: vibration responsive electrical transducer means which has one pair of electrically conductive contact members having contact surfaces mechanically biased in a direction normal to said contact surfaces and thereby held into continuous electrical contact, one of said contact members being of leaf spring construction with its said contact surface being movable with respect to the contact surface of the other contact member in a direction normal to the applied bias when subject to environmental vibration, which vibration is applied directly to at least said one contact member, while said contact surfaces continue in electrical and mechanical surface to surface contact, each said contact member providing an electrical terminal for connection to terminals of the alarm construction, and said contact members defining, in A quiescent condition, a first series of electrical resistance with said terminals and, when subject to direct application of vibration, defining at least a significantly different second electrical series resistance with said terminals, the significantly different values of said first and second series resistances being defined by two different locations of the two contact surfaces relative to one another and independent of contact pressure changes therebetween, if any; a latching switch coupled to be responsive to changes in the resistance of said transducer means and to be triggered as a result of the occurrence of said second resistance; and alarm-producing means coupled to said latching switch and enabled thereby when said latching switch is triggered.

2. An alarm construction according to claim 1 in which there is provided, variable bias control means disposed relative to at least one of said contact members for adjusting the bias of said contact members.

4. An alarm construction according to claim 1 wherein said latching switch has a trigger input coupled to said transducer means, and an enabling switch is arranged in series with another input of said latching switch and said alarm means, to provide electrical energy thereto as well as to said transducer means.

5. An alarm construction according to claim 1 in which conduction means having first and second conductor portions, normally electrically separated, connects said transducer means within said alarm construction by way of said first conductor portion, and resistive means is coupled to said second conductor portion and defines a shunt path with said transducer means in the event of a short circuiting of said conductor portions, whereby said latching switch will be triggered.

6. An alarm construction according to claim 5 wherein said construction means comprises: a shielded conductor of which the inner conductor is said first conductor portion, and the shield is said second conductor portion.

8. An alarm construction according to claim 1 which further comprises: relay means normally positioned to permit said latching switch to be triggered, but when energized, completing a circuit path to an input of said alarm means to enable the latter, while forcing the latching switch to turn off.

10. An alarm construction according to claim 1 wherein alarm timing means are coupled to said latching switch and said alarm means to hold said alarm means enabled a predetermined timed after the triggering of said latching switch.

12. An alarm construction according to claim 15 wherein said amplifier is of the Darlington type, and a second RC circuit is coupled between said first RC circuit and said amplifier to insure that said first RC circuit is fully charged before said amplifier is enabled.

13. An alarm construction according to claim 11 wherein said alarm timing means further comprises: relay means normally positioned to permit said latching switch to be triggered, but when energized, coupled between the output of said amplifier and an input of said alarm means to enable the latter, while forcing said latching switch to be turned off.

15. An alarm construction according to claim 14 wherein: said latching switch delay enabling means comprises conducting means having first and second conducting portions, normally electrically separated, said first conducting portion coupling said transducer means to said latching switch, an enabling switch for connecting said first and second connecting portions, and a delay circuit coupling said second conducting portion to said latching switch.

16. An alarm construction according to claim 15 wherein said delay circuit comprises: a switching element having its output coupled to said latching switch, said switching element having one input coupled to said first conducting portion, and a delay network coupled between said second conducting portion and another input of said switching element.

17. An alarm construction according to claim 16 wherein said conducting means comprises: a shielded conductor of which the inner conductor is said first conducting portion, and the shield is said second conducting portion.

18. A vibration responsive electrical transducer for use in vibration detection apparatus such as tamperproof alarm constructions which include a pair of electrical terminals for connection to said transducer, said transducer comprising: one of said contact members being of leaf spring construction with its said contact surface being movable with respect to the contact surface of the other contact member in a direction normal to the applied bias when subject to environmental vibration, which vibration is applied directly to at least said one contact member, while said contact surfaces continue in electrical and mechanical surface to surface contact, each said contact member providing an electrical terminal for connection to the terminals of the alarm construction, and said contact members defining, in a quiescent condition, a first series electrical resistance with said terminals and, when subject to direct application of vibration, defining at least a significantly different second electrical series resistance with said terminals, the significantly different values of said first and second series resistances being defined by two different locations of the two contact surfaces relative to one another and independent of contact pressure changes therebetween, if any.

19. A transducer according to claim 18 in which there is provided: variable bias control means disposed relative to at least one of said contact members for adjusting the bias of said contact members.

20. A transducer according to claim 18 wherein: at least one of said contact members includes a portion that is irregular in the sense that, at discrete different points thereon, different series resistances can be measured with respect to that contact member.

21. A transducer according to claim 18 which further comprises: an electrically insulating housing constructed to be flush mounted to the surface of a vibration-monitored area, and said transducer is constructed and arranged to be especially compact.