Satellite navigation uses this signal, the GALA signal (pin 1) and an internal laser gyroscope to calculate position in the absence of satellite signals. Mute from Cell-Phone. This pin is used to silence the audio cd, earthed by some other external components such as a mobile phone that is connected to the radio. On some equipment this pin is used, instead, for the rear-view camera control input, which carries the 12v backup-light signal to the head unit to tell it to display video from the backup camera. Note: If the speedometer stops working when the radio is connected, then the pin is probably grounded because radio probably uses this pin for another function, except for GALA. It needs the output from the speed sensor. This pin is used in some radio equipment to automatically boost up the volume.
