Have a customer with 2 of these phones that is determined that she can have Music On Hold without paying the Centrex company to pipe the music down. Sent her a Music On Hold player with regular phone jacks inputs to test and she notified my that her phones use a prong jack. Any advice as to what phone cable end is used and if there is an adapter made to go from her cable to a standard phone jack....or advice in general on adding music on hold to these phones.

Sorry- The only possible way she could add music on hold is to leave the phone off the hook and connect the curly cord to a player with the appropriate adaptors, but that sort of defeats the purpose of "hold" altogether. When you place a call on hold with on one of these sets, the caller is not at your site anymore- they are only connected to the Centrex provider. So there is no way to play music to the caller without the Centrex provider's help at their end.

Thanks.