US3276006A

US3276006A - Audio accumulator

Info

Publication number: US3276006A
Application number: US347761A
Authority: US
Inventors: Donald E Hansen
Original assignee: MOSLER RES PRODUCTS Inc
Current assignee: MOSLER RES PRODUCTS Inc
Priority date: 1964-02-27
Filing date: 1964-02-27
Publication date: 1966-09-27
Anticipated expiration: 1983-09-27

Description

Sept. 27, 1966 D. E. HANSEN AUDIO ACCUMULATOR 2 Sheets-Sheet 1 Filed Feb. 27, 1964 QTTOENEYS.

I IF For mm p 27, 1966 D. E. HANSEN 3,276,006

AUDIO ACCUMULATOR Filed Feb. 27, 1964 2 Sheets-Sheet 2 m- INPUT SIG NAL I l I l I I I RELAY VOLTS I I INPUT SIGNALS TIME 125 31 CHARGE TIME.

\ RELAY VOLTS A T TORA/E Y5.

United States Patent 3,276,006 AUDIO ACCUMULATOR Donald E. Hansen, Brookfield Center, Conn., assignor to Mosier Research Products, Inc., Danhury, C0nn., a corporation of Delaware Filed Feb. 27, 1964, Ser. No. 347,761 1 Claim. (Cl. 340-261) This invention relates to security alarms and is particularly directed to an audio accumulator for use in connection with alarms adapted to be set off by noise or vibration.

One common form of alarm system used to protect bank vaults and other areas to be secured is an audio alarm. In such an alarm, a microphone, speaker, vibration pickup or the like, senses noise such as might be produced by a burglar tampering with a lock, cutting an opening in a wall or the like. When such a noise occurs, an alarm is tripped either locally or in a remote station providing warning that a robbery or other trespass is being attempted.

One of the most difficult problems in connection with audio alarms is providing means for distinguishing between noise accompanying an attempted surreptitious entry and ambient or background noise caused by innocent activity, such as for example by passing vehicles, moving people or objects in adjacent areas or the like.

The principal object of the present invention is to provide an audio accumulator circuit which is highly effective to distinguish between noise or vibration caused by an attempted intrusion and background noise not connected with such intrusion. In essence, then, the present audio accumulator is effective to cause the alarm to be actuated whenever an intruder is attempting to enter the secured area, but at the same time is effective to prevent spurious or false alarms caused by ambient noise.

More particularly, the present invention is predicated upon the concept of providing an accumulator circuit which is effective to cause actuation of the alarm only when a certain quantum of noise is sensed, i.e. a level of noise persisting for a definite time. Specifically, the present accumulator includes means for integrating the noise sensed, both with respect to amplitude and time. The unit operates so that a selected noise will cause an alarm if the noise persists for a predetermined time, for example one tenth of a second. A lesser noise of onetenth the amplitude will cause an alarm only if it persists for approximately one second; and a larger noise, say ten times the amplitude of the selected noise, will cause an alarm if the noise persists for only one-hundredth of a second.

Another object of the present invention is to provide means for automatically resetting the accumulator or continuously wiping its memory clean of events occurring more than a predetermined time in the past. This resetting, or memory wiping, means thus prevents the alarm from being actuated in response to the sensing of a plurality of widely spaced low level noise signals. By way of example, in a given installation there might normally be ten ambient noise events, such as vehicles passing by, doors closing and the like, per hour. However, if ten events of the same level occur within a minute, it would most likely indicate an attempted intrusion. The present audio accumulator is effective to differentiate between the two and to cause an alarm in the latter instance but not in the first instance.

A still further object of the present invention is to provide an electronic, and in a preferred embodiment, solid state audio accumulator which is of relatively simple construction and high reliability in use.

These and other objects and advantages of the present invention will be more readily apparent from a consid- 3,276,6 Patented Sept. 27, 1966 eration of the following detailed description of the drawings illustrating one preferred embodiment of the invention.

In the drawings:

FIGURE 1 is a schematic circuit diagram showing an alarm system embodying a preferred form of sound accumulator.

FIGURE 2 is a diagrammatic view showing the operation of the circuit in response to the occurrence of a single audible event.

FIGURE 3 is a diagrammatic view showing the operation of the circuit in response to the occurrence of a plurality of audible events.

As is shown in FIGURE 1, one form of alarm system embodying the principles of the present invention comprises a sound, or vibration, detector located in the area to be protected, such as a vault or the like. The sound, or vibration, detector 10 may be in the form of a microphone, speaker, or vibration microphone. The pickup device, or detector 10 is connected through a twisted pair of leads 11 and 12, forming part of a shielded cable, to audio accumulator circuit 13. It will, of course, be appreciated that this audio accumulator circuit 13 may be located either in or at a point remote from the area to be protected as desired. The audio accumulator circuit 13 is effective to control the energization of a relay 14 which in turn controls the actuation of an electrically responsive alarm indicated at 15.

More particularly, lead 11 from the transducer 10 is connected to the base 16 of a transistor 17 forming part of the first stage of the accumulator unit. This stage is a generally conventional common emitter audio amplifier stage. Lead 12 is similarly connected to the emitter 18 of transistor 17 through series connected

resistors

20 and 21. Each of the

resistors

20 and 21 is shunted by a capacitor 22 and 23 respectively. A sensitivity adjustment resistor 24 is connected between leads 11 and 12. The other components of this first stage comprise a resistor 25 interconnecting base 16 and collector 26. A positive potential source indicated at 27 is connected to resistor 21 through lead 28, resistor 30 and lead 31. Lead 31 is connected through a capacitor 32 to a common line 33. Line 33 is connected at one end through a resistor 34 to lead 12. The opposite end of line 33 is joined to normally closed contact 35 of relay 14.

The first amplifier stage of the audio accumulator unit is transformer coupled to the second stage which is also a common emitter stage of a generally conventional type used in audio amplifiers. Specifically, collector 26 of transistor 17 is connected to one lead of primary winding 36 of coupling transformer 37. The opposite lead of winding 36 is connected through lead 38 to common line 33. Secondary winding 40 of coupling transformer 37 is connected across a sensitivity adjustment potentiometer 41. Secondary winding 40 is also connected through lead 39 and resistor 42 to lead 38.

Tap 43 of potentiometer 41 is connected to base 44 of transistor 45. A lead 46 is connected to lead 39 and one end of potentiometer coil 41 and to the parallel combination of resistor 47 and capacitor 48. Resistor 47 is in turn joined through the parallel combination of resistor 50 and capacitor 51 to an emitter 52 of transistor 45. A lead 53 is connected to resistor 50 and to a resistor 54 which is in turn joined through lead 55 to a source of positive potential indicated at 56. A capacitor 57 interconnects lead 53 and line 33. A capacitor 58 is connected between collector 60 of transistor 45 and one terminal of potentiometer 41.

This second stage of the sound accumulator unit is transformer coupled to the third stage of the unit which functions as a detector. More particularly, the collector 60 of transistor 45 is connected to primary winding 61 3 of coupling transformer 62. This primary winding is also connected through lead 63 to common line 33. The secondary winding 64 of transformer 62 is connected to 'base 65 of transistor 66. Transistor 66 further includes .an emitter 67 joined through lead 68 to common line 33. .The collector 70 of transistor 66 is connected through lead 71, resistor 72 and lead 73 to a positive potential source indicated at 74.

This third stage of the audio accumulator unit oper- ..ates saturated. Thus, the full supply voltage from source 74 is dropped across collector resistor 72. It is to be .noted that lead 73 is joined through a rectifier 75 to lead applied to" the fourth; or decoupling, stage of the unit.'

Specifically, collector 70 is connected through lead '71, rectifier 8'1 and lead 82 to base 83 of transistor 84. Lead 82 is also connected to a bias line 85 through the parallel combination of resistor 86 and capacitor 87. Line 85 is in turn joined through lead 88 to a source of negative potential indicated generally at 90. An emitter load resistor 91 is connected between line 85 and emitter 92 of transistor 84. The emitter 92 is also connected through resistor 93 and

rectifiers

94 and 95 to the base 96 of transistor 97.

This transistor 97 forms part of the fifth stage. Collector 98 of transistor 84 is connected through lead 100 to collector 101 of transistor 97. Lead 100 is also tied to positive potential source 74. A charging capacitor 102 is connected through lead 103 to the juncture of

diodes

94 and 95 and through lead 104 to line 85. Line 85 is also tied through capacitor 105 to the secondary winding 64 of coupling transformer 62. This same secondary vwinding is also tied to lead 11 through resistor 106 and lead 107.

Base 96 of transistor 97 in the fifth stage is connected to line 85 through capacitor 108. The emitter 110 of .transistor 97 is connected through lead 111 to the winding 112 of relay 14. The other lead of winding 112 is connected to line 85 and negative potential source 90. The fifth stage, including transistor 97, is connected as a common collector amplifier and as such is generally analogous to a cathode follower of vacuum tube circuitry. The load in the form of relay coil 112 is connected in the emitter lead and therefore the stage has no voltage gain. However, the base input resistance is equal to the product of the emitter resistance multiplied by the current gain of the stage. This makes it possible to use a capacitor 102 approximately fifty times smaller than if the stage were omitted and relay 14 energized directly.

Relay 14 has, in addition to stationary contact 35, a normally open stationary contact 113 and a movable contact arm 114. Movable contact arm 114 is connected through lead 88 to negative potential source 90. Contact 113 is joined to output lead 115 of the accumulator. Lead 115 is connected through rectifier 116 to alarm 15. Rectifier 116 is also connected through a second rectifier 117 to conductive switch element 118 which may be in the form of a flexible lead. Conductor 118 is adapted to complete a circuit to contact 120 or contact 121. Cont-act 120 is joined through resistor 122 to lead .71. Contact 121 is joined through resistor 123 to lead 103. It is to be understood that in the normal operation of the unit, conductor 118 engages either contact 120 or contact 12 1, depending upon the type of operation desired. If upon alarm the unit is to latch in that con- .dition, conductor 118 is connected to contact 120. If

the unit is to reset itself shortly after an alarm, conductor '118 is connected -to contact 121. When conductor 118 is in engagement with contact 120 and relay 14 is energized, contact 114 is removed from contact 35, thereby removing battery negative from lead 33 and emitter 67 discharge as shown by line 132. It

of transistor 70. Positive battery current flow is now from lead through resistor 72, resistor 122, conduct-or 11-8, contact and diode 117 to lead 115, contact 113 and contact 114 to battery negative. The volt age established by

resistors

72 and 122 turns on transistor 84 which turns on transistor 97 and holds relay 14 energized. Reset is accomplished by removal of battery voltage.

When conductor 118 is in engagement with contact 121 and relay '14 is energized, the accumulator capacitor 102 is discharged through resistor 123, contact 121, conductor 1'1'8, diode 117 and

relay contacts

113, 114 to battery negative. Diode 95 blocks discharge of capacitor 108 through the above path. Capacitor 108 discharges through transistor 97, holding relay 14 energized until capacitor 102 is fully discharged. i

The operation of the present accumulator circuit can best be understood from a consideration of FIGURE 1 in conjunction with FIGURES 2 and 3. FIGURE 2 illustrates the operation of the circuit in response to a single audible event. When the accumulator unit is in normal operation and senses only a minimal noise level below. a preselected threshold value, the third stage of the unit, i.e., the stage including transistor 66, is operating saturated so that the full voltage from supply source 74 is dropped across resistor 72. Consequently, transistor 84 of stage four is normally nonconducting because of the zero volt potential present on its base 65. (The diode 81 is effective to reject all signals sensed by pickup 10 which are below the selected threshold level.)

When an audio signal above threshold level, such as is indicated by pulse 125, is received a negative pulse is applied to the base 65 of transistor 66. This causes the transistor to drop out of saturation. Thus, the potential applied to diode 81 and hence base 83 is raised. This positive signal passes through the diode and is smoothed by capacitor 87.

When a positive potential is applied to base 83, transistor 84 of stage four becomes conductive. Consequently, a current flows through emitter load resistor 91. A voltage is developed across this resistor which begins changing timing capacitor 102 through resistor 93 and diode 94. The combination of resistor 93 and capacitor 102 have a charge time as indicated by line section 126 in FIGURE 2. Input signal is thus integrated with respect to time and amplitude. The function of diode 94 is to prevent capacitor 102 from discharging back through

resistors

93 and 91 when the positive signal of resistor 91 ceases. I

If the charge on capacitor 102 is sufiiciently high, the fifth stage transistor 97 permits suflicient current to flow through Winding 112 of relay 14 to close that relay. This brings movable contact arm 114 into engagement with stationary contact 113 completing a circuit to alarm 15.

If, however, at the conclusion of the input signal 125 the charge on capacitor 102 is not sutficient to cause relay -14 to close, the accumulator unit automatically begins to wipe its memory as the charge on capacitor 102 decays by discharge through base 96. After a sufficient discharge time, the charge across capacitor 102 is completely dissipated so that the accumulator unit is in effect reset" or its memory is wiped clean.

The operation of the unit when subjected to a series of input signals of shorter duration is shown in FIGURE 3. As there shown, the first input signal 127 causes capacitor 102 to charge in the manner explained above. However, the charge left by this capacitor is not sufiicient to trip relay 14. At the end of the first event 127, the capacitor 102 starts to discharge as indicated by line 128. When the second event 130 occurs, the capacitor again begins to charge as indicated by line 131. At the conclusion of the second event, the charge on the capacitor may still not be sutficient to trip relay 14. Again, at the conclusion of event 130, capacitor 102 begins to is to be noted, however, that when the third event 133 occurs, the capacitor has not completely discharged and hence is starting with an elevated charge which is further increased due to event 133. The signal due to event 133 may be sufficient to raise the charge on capacitor 102 to a point where relay 14 becomes conductive and alarm 15 is energized. If at the end of the third event a charge on capacitor 102 is still not sufficient, the capacitor discharges in the manner explained above until it is brought back to a zero potential.

From the foregoing disclosure of the general principles of the present invention and the above description of a preferred embodiment, those skilled in the art will readily comprehend various modifications to which the invention is susceptible. Therefore, I desire to 'be limited only by the scope of the following claim.

Having described my invention, I claim:

In an alarm system including an audio or vibration pickup effective to produce an electrical signal and alarm means, the combination of a detector for said electrical signal, a buffer transistor connected to said detector, an audio amplifier transistor including a base and an emitter, a series circuit comprising an integrator resistor, and first and second rectifiers for conducting current in one direction interconnecting said detector and the base of said audio amplifier transistor, an integrator capacitor for receiving a charge through said first diode interconnected between the junction of said first and second rectifiers and a reference potential, a second capacitor connected inter-mediate said second rectifier and the base of said amplifier transistor for receiving a charge through said second diode, a relay including a winding interconnected to the emitter of said amplifier transistor, said relay having first and second stationary contacts and a movable contact connected to said reference potential, said movable contact being in engagement With said first contact when said relay is deenergized and being in engagement with said second contact when said relay is energized, a second resistor connected to the junction of the first and second rectifiers for regulating the discharge of said integrator capacitor at a first rate, a selectively operable switch etfective to interconnect said second resistor to the second contact of said relay, said second capacitor having a discharge circuit through said amplifier emitter for discharging therethrough at a second rate slower than the rate of discharge of said integrator capacitor, whereby when said selectively operable switch interconnects said second resistor and second relay contact and said relay is energized, said integrator capacitor is fully discharged prior to the discharge of said second capacitor and deenergization of said relay.

References Cited by the Examiner UNITED STATES PATENTS 2,435,996 2/1948 Baird 340-258 2,655,645 10/1953 Bagno 340-258 X 2,767,393 10/1956 Bagno 340258 2,942,247 6/1960 Lineau 340261 X 3,017,543 1/1962 Hillman 317148.5 3,134,970 5/1964 Kelly .a 340261 3,147,467 9/1964 Laakman 340-261 NEIL C. READ, Primary Examiner.

R. M. GOLDMAN, Assistant Examiner.