This circuit was found in a Popular Electronics from the 90s. The circuit has 4 frequency ranges selected according to the capacitors. Signal is rectangular.
This speed or priority switch set uses two LED indicators and two SCRs in a common configuration. The...
Found in a 90s American documentation, this circuit is used in vehicles with contact breaker. The...
This circuit for activating a relay was found in a Radio Electronics magazine from August 1962. The...