This circuit was found in a 90s Popular Electronics. The circuit uses 4 bicolor LEDs to indicate signals of both TTL and CMOS logic. The circuit is powered by the source of the circuit under test.
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...