This circuit was obtained from an American technical manual from the 80's. The integrated circuit is an operational of the time that can be replaced by a modern equivalent.
We found this circuit in the old Mullard transistor reference manual from 1960. The circuit is...
This circuit was obtained in a Portuguese publication in 1979 but can be easily assembled today by the...
This circuit was found in a European publication from the 1980s. The transistors can be the BC548...