The signal tracker is a modified version of the 1kHz function generator and has it’s own speaker.
With the signal tracker you can test if OPAmps and amplifiers are working properly. Via Cinch-connectors you can either take the 1kHz sine wave or the 1kHz square wave and connect it to your circuit. If you then probe the circuit and the signal is passing through the circuit correctly, a pre-amplifier on the tracker is boosting the signal a bit and outputting it to the speaker.
All signals can be raised or lowered with some potentiometers, the sine wave output and the signal input both are decoupled with a capacitor.
As usual schematic and some pictures.