This wired intercom circuit was found in an English publication from the 80's. The integrated circuit can be replaced by an equivalent, just like the transistor which is a general-purpose type.
Found in Motorola's 1965 manual, this full-wave dimmer controls a load that depends on the used...
Found in American documentation from the 90s, this circuit uses components that are still common...
This relaxation oscillator with solid-state triggering element was found in an old European...