This circuit is from the time when slide projects were used. We find it in a 90's Wels’ Think Tank. The lead times can be adjusted from 5 to 30 seconds.
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...