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 operates at a voltage of 1.3 V from a single mercury cell. We found in an old...
April 2017 - Mouser Electronics already has in stock the new HMC8400, Analog Devices low noise...
This circuit was found in documentation by Linear Technology from the 90's. The circuit makes...