This simple metronome, from 1985 documentation uses only transistors and has two settings. For voltages above 6 V, up to 12 V, replace the BC557 with a BD136.
This simple circuit allows the monitoring of both audio and RF signals. With the switch in one...
This circuit was found in documentation from the 1980s. The integrated circuit used is uncommon today...
With a light pulse on the Q1 sensor the circuit turns on and locks. To switch off, a light pulse...