This circuit was found in Philips documentation from 1967. The components are of the time, being transistors like BCY38 for TR1, BC108 for TR3, and others depending on currents.
This circuit, found in documentation from the 1990s, uses a common 7-segment LED display. The...
This circuit can be used as an answering password system in a store, office, or other location....
This circuit was obtained from a Popular Electronics of 1994. The magazine no longer exists in its...