This continuity test was found in a 90s Electronic Engineering. Transistors are types of general use of the time with equivalents such as BC548 and BC558.
This circuit is from a Radio Electronics from March 1970. The crystal depends on the frequency at which...
This circuit detects magnetic fields through a sensor coil, providing a signal in its function. The...
Described in an article that taught how to assemble the complete intercom in Radio Electronics magazine...