This car alarm was obtained in a Signetics documentation from the 1980s. The circuit uses the 555 and has a pulsed output to activate a relay that controls the horn. The sensors are parallel connected.
This circuit was found in a 1992 PE Hobbyst. The circuit detects the presence of spy...
This configuration is suggested by Mullard (Philips) in an old manual of 555 integrated circuits....
Common operational amplifiers like the TL series, CA3140 and others can be used in this circuit...