This OF-1 LO oscillator was found in a 1980s American documentation. The transistor can be any general-purpose and C1 / C2 are determined by the frequency.
This circuit is from a 1980s Motorola documentation. The circuit can be made with modern...
This well-known circuit triggers a relay when light striking the phototransistor is cut off. The...
This circuit generates a pulsed tone whose frequency depends on C2 and whose flashing depends on...