Chirp mute timer circuit for car alarm systems such as SPY

Eliminated the annoying chirp with a circuit based on an NC7SP14 Schmitt Trigger that has an input delay set by a capacitor of 10uF and switches a mosfet that pulls down the base of the transistor inside the remote that is the amplifier for the beeper. This particular remote uses an electromagmetic transducer, not a piezo. It could however also be used for a piezo, but then in a different way. The circuit uses just a few microamps of power, so will not noticeably affect the battery life. I have used the display backlight to trigger the delay, as the backlight is always on when it does anything chirpy. When there is an actual alarm, or when you just press the open button repeatedly, eventually you will hit the threshold of the Schmitt Trigger and open up the sound. Any shorter term chirps however are 100% eliminated! Modifications to remotes can perhaps also be done, I shall look in to it and maybe design a proper PCB for it, then waterproof it and maybe build it in your remote at some point in the future as a service. The size of the entire circuit board will be maybe 1x1cm and 3mm thick. It uses four wires, + and - a mute output wire to connect to the base of the amplifier transistor and a trigger input that can be connected to various things, the capacitor voltage will be at around 2 volts to reach the threshold, but that can be modified lower or higher.

Here are the schematics:
kadett-forum.de/core/attachment/63048-spy-remote-silencer-clean-png
(what is in the green box was already present in the remote)

Видео Chirp mute timer circuit for car alarm systems such as SPY канала Vincent de Groot