This sequential tone generator circuit was found in the July 1980 issue of Radio Electronics magazine. It uses well-known integrated circuits. The tones are generated by programming resistors.
This receiver was found in a 1968 publication, but can be mounted with a BC548 and BC558 in place...
Found in 1965s General Electric documentation, this circuit is intended for the control of servos...
The integrated circuit used in this 90's circuit is not very common today. An equivalent...