This circuit was found in a 1967 Electronic Design. The FET is from that time. Capacitor C is determined by the frequency of the signal worked.
This light sensor shield, with operational and TTL compatible output or microcontroller was found...
This circuit is from a 1980s Motorola documentation. The circuit can be made with modern...
The number of pulses produced by this circuit depends on the switch pressed. The circuit is from...