Extension (Slave) Socket. You are allowed to install extension wiring so long as the connection to the master socket is via a plug, or in the case of the master socket with a detachable lower half, via the connectors on that section.
3m Genuine BT Black 2 pair 4 wire Telephone Cable CW1308 Blue Green Brown Orange
50m Black 2 Pair External Telephone, BROADBAND / DSL Extension Kit
50m 2 PAIR BLACK External Telephone Cable Extension Kit copper tool socket clips
2 PAIR 100MTR External Black Telephone cable, BROADBAND / DSL Extension Kit
15m Genuine Black EXTERNAL 2 pair 4 wire Telephone Cable BT Spec CW1728