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.
Using 18 or 24 MHz crystals, this circuit is intended for producing reference signals with...
This circuit can source 3 to 12 V with currents up to 500 mA depending only on the transformer....
Another alternate action switch that uses a NAND Schmitt Gate [4093 IC] is shown here. The...