We found this circuit in the 1989 Radio Electronics Experimenter. The circuit uses common components, and the thermistor is supposed to determine the value of the trim potentiometer.
The circuit shown, found in a 2004 documentation, allows the use of a telephone, without the...
This simple circuit needs a high gain stage to compensate for losses. It consists of a passive tone...
The time constant for this circuit found in a 1973 publication is given by R and C. The shot is...