This circuit was found in a 1967 American documentation. The switching diode (tunnel) used is an uncommon component today.
If you have old tube or transistor amplifiers that hum (60 Hz noise) the circuit shown may be the...
June 2017 - The new touch screens with resistive sensors of the FK Series from NKK Switches can...
July 2017 - Microchip's new MCP9V91 operational amplifiers with input offset and low drift voltage...