This Philips circuit of the 70's makes use of components of the time. The DZD40 is an uncommon integrated circuit today.
This commercial circuit is from a Japanese magazine from 1967. It uses germanium transistors, and...
This circuit can be used to drive relays, solenoids, motors and other loads according the...
This circuit is based on the small keychain that responded to the sound of a whistle and were...