The integrated circuit used in this amplifier is not very common today. This amplifier was found in the 1977 National Semiconductor Audio Handbook. The power source must be at least 500 mA.
This code switch was found in a 1990 Electronics Handbook. It can be mounted with BC558...
In this application we use an additional input circuit to enable the logic command with keys,...
This circuit was suggested by Signetics in 1980s documentation. The circuit makes use of the...