I need to send audio 2 wire or 4 wire between two 1760's via the E&M ports. These do not hook up to a PBX and no telephone operation is used at all. Basically I have equipment at Location A which needs to communicate with Location B via the E&M ports. The equipment at each location sends a reference to ground signal when receiving and can receive a reference to ground when transmitting. I do need some help interfacing as I do not have typical -48v signal line availiable. Thanks