Automatic tamper alarm for motor vehicles

• US 3,930,226 A
• Filed: 04/22/1974
• Issued: 12/30/1975
• Est. Priority Date: 04/22/1974
• Status: Expired due to Term

• Current Assignee: Leonard G. Plumberg
• Original Assignee: Leonard G. Plumberg
• Inventors: Plumberg, Leonard G.
• Primary Examiner(s): Waring, Alvin H.
• Application Number:
  US05/462,659
• Time in Patent Office: 617 Days
• Field of Search: 340/52D,52F,63,64 307/1AT 180/114
• US Class Current: 340/430
• CPC Class Codes: B60R 2325/304 Boats
• CPC Class Codes: B60R 25/1003 Alarm systems characterised by arm or disarm features
• CPC Class Codes: B60R 25/1004 Alarm systems characterised by the type of sensor, e.g. current sensing means using door lock sensors B60R25/1001

Abstract

A self resetting tamper alarm activates a motor vehicle horn when one of a plurality of input lines detects the closure of a normally open switch. The solid state alarm is a low current device which may continuously be left in a triggerable state without undue expenditure of the vehicle battery, and it is automatically disabled whenever the vehicle ignition switch is turned to '"'"''"'"''"'"''"'"'on'"'"''"'"''"'"''"'"' or '"'"''"'"''"'"''"'"'accessory.'"'"''"'"''"'"''"'"' The alarm comprises a monostable multivibrator with a time constant in the order of a few minutes. In response to an alarm input this multivibrator generates a trigger signal which activates succeeding circuitry, eventually energizing the horn. The trigger signal ceases after a few minutes in accordance with the multivibrator time constant to avoid unnecessary run down of the vehicle battery, but it will again occur if an alarm input is subsequently presented after the multivibrator resets itself. An astable multivibrator generates a square wave output in response to the aforementioned trigger signal. This square wave output is amplified and delivered to the vehicle horn to provide a pulsating (rather than continuous) tone therefrom. In addition, delay circuitry is provided to prevent activation of the alarm for up to a minute after a signal has occurred on preselected input lines. Thus, after opening the car door, the operator has a preselected time to enter the vehicle and prevent horn activation by turning the ignition switch to disable the alarm. Another delay circuit integral with the one shot timer also allows the driver to stop the car and exit therefrom without triggering the alarm. For various other inputs however, the first delay circuitry is inoperative and an immediate alarm response will occur unless the alarm has been disabled.

Claims

1. A tamper alarm for motor driven vehicles for activating an external transducer in response to preselected events, the alarm having an output and functioning in cooperation with the vehicle ignition switch, the alarm comprising:

a plurality of alarm input means for initiating alarm circuitry operation in response to inputs delivered thereto;

means for generating a trigger signal for a predetermined time interval in response to at least one of said alarm inputs, the trigger signal generation means comprising a monostable multivibrator having at least one input and an output, one of said monostable multivibrator inputs interconnected with said alarm input means;

means for generating an intermittent output signal for said external transducer in response to said trigger signal, the last mentioned means comprising an astable multivibrator having at least one input and an output, the astable multivibrator inputs interconnected to said monostable multivibrator output, means for interconnecting said astable multivibrator output with said external transducer, means cooperating with the vehicle ignition and/or accessory switch for automatically disabling said alarm whenever said vehicle ignition and/or accessory switch is activated, said monostable multivibrator comprising at least one NOR-gate having at least one input and said alarm disabling means further comprises an interconnection between said vehicle ignition and/or accessory switch and said NOR-gate input, the interconnection operable to disable said monostable multivibrator by turning off said NOR-gate when said ignition switch is turned to the ignition on or accessory position.

2. The combination as in claim 1 including means for delaying the response of said alarm for a preselected time after said ignition switch is turned off, the last mentioned means comprising a capacitor connected between ground and said monostable multivibrator input, the capacitor operable to charge when said vehicle ignition/accessoRy switch is on and discharge when said vehicle ignition/accessory switch is off, the response of said monostable multivibrator thereby being delayed until said capacitor substantially discharges.

3. The combination as in claim 2 wherein said delay means further comprises means for inhibiting said intermittent alarm output signal generator for a preselected time after an alarm input, the last mentioned means comprising a capacitor connected between ground and one of said astable multivibrator inputs, the capacitor operable to charge when said monostable multivibrator output is high and discharge when said monostable multivibrator output is low, said capacitor preventing said astable multivibrator from functioning until it is discharged to a preselected level.