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.
We found this configuration in the ON Semiconductor thyristor manual. The triacs depend on the...
This circuit was found in an old documentation. It converts DC voltages and its maximum current...
This circuit makes use of comparators and common operational amplifiers, having been found in...