Great, I will check out Dynametrics web page. I also found a device from JK Audio called the THAT-2 (Telephone Handset Audio Tap) that goes between the handset and the phone, and has an RCA input to bring in an outside audio source. We haven’t tested it yet, but it looks like a good tool. It is supposed to work with Electret, Carbon and Dynamic Handsets (there is a selector to pick the type of handset that you have).
Thanks for the Tip on Dynametrics, I have used their Logger Patches in the past, and they worked well.