Found in a Popular Electronics from the 80's, this circuit makes use of a time integrated to control a relay in a timed way. R2 determines the activation time.
This is a possible setting for a Colpitts oscillator operating in the audio track. The shunt coil...
We found this circuit in a European publication of the 1980s. The transistor could be the BC549. The...
This programmable circuit emits a signal that can be sensed by the dog at a distance. The circuit is...