This circuit with an unusual configuration was found in the January 1974 issue of Radio Electronics magazine. The frequency is given by L1/C1, and the transistors admit equivalents.
This circuit transmits beeps to receivers tuned in a wide range of frequencies placed nearby. The...
After starting, this circuit turns off the relay in a time that depends on the 4020 pulse-count. This...
This simple circuit can use general purpose transistors and SCRs like the TIC106. The warning...