This two-tube circuit, one being a double, was found in Radio Electronics magazine from July 1958. The distance to the microphone depends on noise and losses. The cable must be shielded.
This filter is suggested by the Texas Instruments Linear Circuits Applications, 1986 edition. The...
With each touch on S1, an output of 4017 is activated, this in sequence 3, 2, 4, etc. These...
This inverter for 230V (220V) loads was found in the 2021 Internet documentation and is based on...