This circuit uses an amplifier from National Semiconductor, uncommon nowadays. The numbers in parentheses are for the second channel. The circuit is suitable for old tape recorders.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...