The transistors of this circuit found in an English 1980s documentation may be the modern BC548 equivalents. The circuit is battery powered and the earphone must be crystal.
The integrated circuit used in this amplifier is not common today. The power can be between 4 and...
This circuit was obtained from a 1997 publication. It is an alarm that has a lock and a bistable...
We found this circuit in a 1991 publication. What it does is to amplify a signal with unit gain...