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.
July 2017 - Texas Instruments' new 3 A bq25601 single cell battery charger can be found on Mouser...
This circuit was found in old documentation. PUTs are uncommon components today. The circuit...
This simple timer with unijunction transistor was found in an old American technical...