This circuit uses a capacitor that depends on the frequency of the crystal. We found it in a 1967 documentation. The maximum frequency is around 100 kHz.
This control panel allows the use of NO and NC sensors, turning the alarm on after 30 seconds...
We find this filter with three operational of the time in an American documentation of the 80s....
The Texas TL783 integrated circuit is a three-terminal high voltage regulator with a wide range of...