This static switch or triac contactor was obtained from Philips 1969 documentation. The SCR is from the era, but modern equivalents depending on the load can be used.
This power supply was found in a RCA publication from the 1970s. The circuit uses transistors from that...
This very high input impedance preamplifier is from a publication of 1977 but can also be mounted...
This circuit was found in an Electronic World of 1968. The circuit uses power transistors of the...