I have a customer that has a phone system with Music On Hold connected to a radio. The MOH wasn't sounding as clear as they liked so they purchased a digital radio hoping it would help. The radio sounds great, but when it is attached to the phone system, it still sounds bad.
I don't know too much about phone systems, but most of the MOH systems I've dealt with just had a headphone jack on the system you plug a radio or player into.....this one is different.
Instead, it looks like they split the headphone cable from the player and connected to an Ethernet cable which goes to the phone system.
If you look at the attached picture, the black cable is what goes to the new digital radio, and the grey cable gets plugged into the phone system in what looks to be an Ethernet Port. There is nothing that gets plugged into the actual phone port on that jack.
To me, it seems like the black and yellow cables connected to the actual RJ11 port should be removed, or better yet, bypass that jack and use an IDC connector like this: http://www.homedepot.com/p/Klein-Tools-UR-IDC-Connector-for-UR-19-26-AWG-VDV826-605/203579185#