The selected circuit was found in GE's 1977 semiconductor manual. 3N84 is a controlled silicon switch and SCRs support equivalents. The transistor can be a BC558, depending on the supply voltage.
This circuit can use 20 to 100 mA relays with a general-purpose transistor such as the BC538. The...
The tone control in the figure below can be implemented with almost any operational amplifier. The power...
This circuit was found in a 1967 General Electric documentation. The components are from that...