Hi there,
Maybe you can opt for a software equivalent to set your music on-hold system instead of using a bi-directional device. But search for Music Tel Net a device that can also be LAN connected.
I'm looking for a Music-on-Hold Device that is bi-directional.
Here is the reason: I need to transfer audio content directly from my
digital telephone onto my Mac computer. Note that my telephone has an answering machine built into it, but I don't have the PBX system.
So I'm using the Music-on-Hold box as a way to do the transfer. Once on my computer, I'll work with the audio content as an mp3 file.
I've been looking at the OHP 6500 Music-on-Hold unit, but I'm not sure if it's bi-directional or not.
Note that I don't have the 3CX VOIP Phone System, but I haven't been able to find a more suitable forum for my question.
Thanks for any tips.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic