[Asterisk-Users] MOH from RCA jack?

[Rich Adamson]

Been around asterisk for two-plus years, but need a little input from the
list on this topic.

Have a potential client that wants to replace their old key system with *,
but they want to integrate a commercial message service (they pay a monthly 
fee to have special MOH messages generated) into their system. The messages 
are essentially delivered to this customer via older generation audio 
equipment that interfaces to their key system via a standard audio RCA jack.
(We're reseaching other alternative deliver mechanisms such as mp3's, etc, 
from the supplier, but have to assume for now that we need to inject MOH 
audio into asterisk via this RCA jack.)

Does anyone have a relatively high audio quanlity method of interfacing 
such an external audio device into asterisk in a reliable way via an
RCA jack?