Automobile theft alarm with ignition controlled automatic arming means

• US 3,956,732 A
• Filed: 01/02/1973
• Issued: 05/11/1976
• Est. Priority Date: 01/12/1972
• Status: Expired due to Term

• Current Assignee: Harrison Systems Incorporated
• Original Assignee: Rudor M. Teich
• Inventors: Teich, Rudor M.
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Nowicki, Joseph E.
• Application Number:
  US05/320,542
• Time in Patent Office: 1,225 Days
• Field of Search: 340/63, 340/64, 340/276, 340/274, 340/213, 307/10 AT, 180/114
• US Class Current: 340/430
• CPC Class Codes: B60R 2025/1013 Alarm systems characterised by the type of warning signal, e.g. visual, audible
• 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
• CPC Class Codes: H03K 3/351 the devices being unijunction transistors H03K3/352 takes precedence

Abstract

A vehicle warning system is automatically armed via the ignition switch each time the ignition is turned off and the key removed so that no positive action of the driver is required. The system may be disabled between authorized uses of the vehicle through the ignition switch by turning to the accessory position. However, the arming circuit is so designed that the procedure may be reversed merely by reversing a lead connection at the time of installation.

The system is equipped with two sensing circuits one of which is adapted to sense the energization of a resistive load device and the other of which directly senses the opening of the hood and/or the tampering with selected areas of the vehicle protected by a closed loop circuit. A novel latching circuit is designed to selectively provide holding current for a latching SCR operatively connecting both sensing circuits to the alarm energizing circuitry and includes a field effect transistor controlled by the voltage level at its gate terminal provided through an RC network. That network provides a relatively long exit delay upon turning off the ignition during which the circuit will not latch in addition to an automatic alarm shutoff feature designed to unlatch the circuit after it has sounded for approximately five minutes. Manual switch means operatively connected to the aforementioned latching circuit is provided for permanently preventing the circuit from latching thereby to disable the circuit on a continuous basis without compromising the security of the circuit.

The alarm energizing circuitry is provided with an inherent entrance delay with means to bypass that delay when the cause of the alarm is other than the opening of a door of the vehicle. In addition, means are provided for bypassing the entrance delay and latching circuit completely regardless of the condition of the vehicle door in response to the actuation of the hood and tamper sensing circuit.

Finally, means are provided for maintaining the rate-of-change of battery voltage sensor insensitive to the turnoff of the vehicle headlights to account for delayed automatic headlight turn-off as is found in some late model vehicles.

Claims

1. For use in a vehicle having a power supply and an ignition switch having at least first, second and third operative positions, a vehicle alarm system for providing an alarm in response to unauthorized entry of the vehicle, comprising means producing an alarm signal in response to said unauthorized entry, alarm means, alarm energizing means connected in operative circuit arrangement with said alarm means, and adapted when activated to energize said alarm means to produce said alarm, means adapted to sense said alarm signal and effective, in response to an alarm signal so sensed, to activate said alarm energizing means, first and second lead lines, said ignition switch, in said first position, being adapted to connect said first lead line to said power supply, in said second position to connect said first and second lead lines to said power supply, and in said third position to disconnect said first and second lead lines from said power supply, disarm means operatively connected to one of said first and said second lead lines and to said alarm energizing means and adapted to be activated by said power supply and when so activated to disarm said alarm energizing means to prevent energization of said alarm, said disarm means, once activated, normally remaining latched in its activated condition to maintain said alarm disarmed, and means operatively connected to said second lead line to prevent said disarm means from latching when said ignition switch is in said second position.

2. The alarm system of claim 1, wherein said disarm means comprises a first switch means having a control terminal and an output circuit operatively connected to said alarm energizing means and adapted when conductive to disable said alarm energizing means, said control terminal of said first switch means being operatively connected to said one of said lead lines, and wherein said latch prevent means comprises a second switch means having a control terminal and an output circuit operatively connected to said alarm energizing means in parallel with said first switch means, the control terminal of said second switch means being operatively connected to the other of said lead lines, said first switch means when its control terminal is operatively connected to said power supply being adapted to latch provided sufficient holding current flows therethrough, said second switch means when conductive depriving said first switch means of its holding current thereby to prevent said first switch means from latching.

3. The alarm system of claim 2, wherein said first switch means comprises a silicon controlled rectifier.

4. The alarm system of claim 2, further comprising capacitive storage means and resistive means operatively connected in parallel between said control terminal of said second switch means and ground, whereby when said ignition switch is switched out of said second position said second switch means is maintained conductive for an interval determined by the time required to discharge said capacitive storage device through said resistive means.

5. A vehicle alarm system for use in a vehicle having a power supply and headlights comprising an alarm, sensing means operably connected to the power supply for generating an alarm signal upon the energization of a resistive load device, means operatively connected to said alarm for activating said alarm in response to said alarm signal, delay means operably connected between said activating means and said sensing means for delaying said alarm signal generated by said sensing means, switch means operably connected to at least one of the doors of the vehicle, means operably connected to said switch means to disable said delay means when at least one door remains closed, and means operably connected to said sensing means and to said headlights to disable said sensing means while said headlights are on and for a short interval after said headlights are shut off.