This circuit is powered by a voltage of 4.5 V, being common in radios of the 60's. The circuit is from Mullard's transistors reference manual.
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...