Acoustic indicator
A signal will be heard on the audio system when a message is shown on SID. If there is more than one message, only the first will be indicated acoustically.
ICM is the controller for acoustic warning and indicator signals, which means it determines the priority and activates the audio system.
ICM receives a bus message to generate an acoustic signal and transmits a message on the O-bus requesting an acoustic signal in the loudspeakers. EHU (the main radio unit) receives the bus message and sends an acoustic signal to the front speakers.