I NEED TO CONNECT A 2nd MOH SOURCE ON A 128 Ver.6.03.I own a programmer kit.ON THE MPD, VOICE CHANNEL NO. 3 IS FREE WHERE CAN I FIND ON THE MDF,AND WHAT CHANGES I HAVE TO DO ?

Voice channel 3 is on the red blue pair and the red orange pair on the MPD cut down. But you might have to put it on the Red Blue pair cause that's the in. This channel iss normally used for the door unit or external paging. But I never tryed to put a second MOH on it. I've always added an OCD with a MIM.

Let me know if it works.

You will need a OCD and MIM as Tony stated VC3 is for paging. There is a RCA connector on the front of the MIM that is the first VC on the MIM. Makes for easy MOH connection.