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 circuit is from the LM101 manual. However, the configuration is valid for other operationals. The...
September 2016 - It can be obtained from Mouser Electronics a kit for developing wireless remote...
The operational amplifier of this circuit can be the 741. The circuit has very low consumption and can be...