Partyline: IFB Controller
Clear-Com offers a range of partyline IFB products
MA-704 (current)
4 channel IFB Control Panel with Microphone Jack (6.3" X 1.7"), for console or optional rack mount.Connects to a IFB controller PIC 4704
Obsolete unit MA-4
The MA-704 uses a plug-in Gooseneck Microphone (GM-18 or GM-9)
The MA-4 has a Gooseneck Mic already attached to the unit
http://www.clearcom.com/product/partyline/program-interrupt