Art of Electronics 3rd ed. Figure 2.37
green: sinewave input with -180° phase
yellow: sinewave input with 0° phase
blue: sinewave output with phase 0°-180° determined by the variable resistor.
This circuit gives (for sinewave input) an output sinewave of adjustable phase (from 0° to 180°) and with constant amplitude.
The phase shift depends on the frequency of the input signal for a given setting of the potentiometer.
