Audible antitheft alarm for motor vehicle - has timing circuits to allow driver to alight before operating, and utilises door operated contact to actuate capacitor charging circuit

摘要

The antithief device is for a motor vehicle and provides an audible alarm signal whose sound is different according to the manner in which it was intitiated. This avoids confusion with the operation of the vehicle horn. A contact in the interior light switch is closed when the vehicle door is opened. This allows a capacitor to charge with a time constant of 20 seconds. This action allows a second capacitor to charge through a variable resistor to provide a timing circuit for the entry time. A parallel resistor set timing for the alarm duration. An output timing circuit has a parallel capacitor and resistor circuit which allows the driver time to arm the circuit and alight from the vehicle. A multivibrator operates a relay which controls an audible sound unit to produce a modulated signal.