This circuit is from a documentation from the 70s. The circuit uses logic gates of the time, which in many cases were arrays of transistors allowing use as audio amplifiers, as in this case.
This configuration is from a 1987 publication, but it can be easily assembled today, as the...
This is a simple source indicated for powering low voltage projects on the bench. The circuit is...
This circuit is from Philips' 70s documentation. Transistors can be replaced by modern...