In the United States, when Blueworx Voice Response is connected to a central office switch via a T1 trunk, the connection must be made through a channel service unit (CSU). The CSU protects the circuit against power surges and allows the telephone company to test the trunk.
You might also need a CSU if you connect Blueworx Voice Response to a PABX or channel bank. When Blueworx Voice Response is located more than 15 meters (49.5 feet) from a PABX, channel bank, or a powered repeater, a CSU is required to complete the connection.
Blueworx Voice Response works with any FCC-compliant CSU.