RJ11 male plug to RJ45 socket converter/adaptor, converts an RJ45 8 way plug to an RJ11 4 way. Enables the use of CAT5 & CAT6 Ethernet cables for the connection of ADSL routers & modems to the ADSL service (Most routers & ADSL filters have RJ11 sockets for the ADSL connection). Can also be used for other telecoms applications. The centre 4 pins of the RJ45 socket are connected straight through to the RJ11 plug. If you require a matching opposite to this converter (ie, RJ11 female to RJ45 male) our type C converter available below is the correct part. It has become common for non telecom applications such as low voltage lighting control systems & central heating controllers to utilise RJ series plugs, these adaptors are suitable for these systems.