Chris Mac Gregor
The effect of the Talk Box is that of the speaking or singing of the instrument. This is obtained by inserting a plastic hose into the mouth and singing the guitar (or other instrument) sound directly into the microphone. The effect can be combined with other effects and has a built-in power supply and amplifier.
When you switch it on with the rectangular rubber footswitch, the red LED dims and a blue led located at the base of the rubber hose turns on, the sound goes to a signal amplifier and an internal speaker connected with the hose. At the same time the output is disconnected, so the signal only goes through the hose, not to the guitar amplifier.
When you turn it off, the blue LED (at the base of the hose) dims, the red LED turns on, the amplifier is bypassed and the signal goes to the guitar amplifier again.