It plugs in series with the headset plug under the left pocket. It has a 3.5 mm plug for the audio input from a GPS, phone or whatever has that type of jack. The sound is only going to the headsets because it is just like another input to the intercom. It mutes the radio or cassette while the sound from that jack is playing.
Yes you can use it for mp3 music sources but it will only be in mono. The intercom is not set up for stereo.
Yes you can use it for mp3 music sources but it will only be in mono. The intercom is not set up for stereo.
