Wiring Information - Telephones UK Wiring Diagram for Master & Extension they also have a small coil in series with the 'bell wire' on pin 3 which acts as a filter. On older installations (pre-1980) cream or grey cables were used Wiring Colours for CW1311 Internal 4/6 Way Telephone Cordage : normally used to 6 Pin Trailer Connector Wiring Diagram Collection | Wiring 6 Pin Trailer Connector Wiring Diagram Collection - Trailer Lights Wiring Diagram 6 Pin. Hopkins Trailer Wiring Diagram Natebird. Wiring Diagram for Trailer Save 7 Prong Trailer Plug Wiring Diagram. Trailer Wiring Diagram 7 Wire Circuit Truck to Trailer.