The circuit shown is from the 1977 GE semiconductor manual. More modern equivalent SCRs can be used. R1 must be wire type.
This circuit, from the 70's, can be assembled with a more modern FET like the BF245. The circuit is...
We found this telephone amplifier in a European publication from the 1980s. The transistor can be...
This is the factory setting (National Semiconductor) of the TDA2006 as an audio amplifier. The...