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.
This circuit has already been explored in other articles on this site. It shows how we can use two...
This small control for DC motors up to approximately 1 A uses an operational amplifier that admits...
As in the previous case (CB5045E), we have in the circuit of the figure the use of the polarized...