This circuit was obtained from an Electronics Now from the 90's. It generates the dial signal and the ring tone, serving for testing as well as for demonstrations.
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...