Audio signal generators produce signals in a range from a few Hertz up to several Kilohertz.
Signals can be injected into audio amplifiers to see how they behave at various audio frequencies.
Amplification and frequency response can be measured and distortion of the signal can be observed.

Radio frequency generators can provide frequencies from about 100 Kilohertz up to several hundred Megahertz.
With radio frequency generators it is usually possible to modulate the R.F. with an audio signal to simulate a radio station. Amplitude and frequency modulation are available.
Using an R.F. generator the various tuned circuits in a radio can be adjusted for peak performance.

The picture is of a simple generator with on/off and frequency and amplitude controls. The large control knob in the centre selects the base frequency while the four switches below select a multiplier.
For example if the base frequency is 30 Hertz and the multiplier is X10 then the output signal is 300 Hertz.

Generators producing square waves, sawtooths and triangular waves etc are called function generators.

Generators can be used in the location of faults in non-working equipment. See the page on fault finding.