T1 Physical Specifications

Within the communications network twisted pairs are used. One pair for transmit, and another for receive making four wires for each T1. This allows T-carrier systems to transmit and receive simultaneously in both directions at full speed (full duplex).

A Channel Service Unit / Data Service Unit (CSU/DSU) is frequently used for receiving T1 communications. The CSU/DSU is used to convert the 4-wire digital information into a serial connection (typically RS-449 or V.35). These serial connections are then patched into either voice systems such as a PBX, or into a router or other data networking device.