Patent ID: 6040761
Filing Date: 2000-03-21
Classification: B60R,G07C

Abstract:
In combination with a motor vehicle having a remotely operable subsystem, a system comprising:an acoustic emitter on the vehicle set to emit a low-frequency sound to indicate a condition of the subsystem;a microphone on the vehicle picking up ambient sound and producing an output corresponding thereto;signal-processing means connected to the microphone and including a low-pass filter for filtering from the output sounds of a frequency above the low frequency of the emitter, an amplifier for amplifying the filtered output, and a rectifier for transforming the amplified filtered output into an analog output having a level corresponding to a level of low-frequency sounds picked up by the microphone;an oscillator;a variable-gain amplifier having an input connected to the oscillator and an output connected to the emitter; andcontrol means receiving the analog output from the rectifier and connected to the variable-gain amplifier for setting an output volume of the emitter proportional to the level of the analog output.