This reinforcing stages from a 1960s documentation. No information is given about the transformer and the transistor admits equivalents.
This circuit, from a former publication of 1968 was originally designed for germanium transistors, but with the...
The circuit is from the Texas Instruments optoelectronics manual. The capacitor depends on the...
This circuit was found in a 1960 transistor manual from Sylvania. The components are from that...