RJ11 male plug to RJ10 socket converter, converts an RJ10 4 way plug (4P4C) to an RJ11 4 way plug (6P4C). Can be used for various telecom applications, eg, connecting a headset with an RJ10 plug to a phone with an RJ11 socket. Note the RJ11 plug will plug into an RJ12 socket however RJ12 is 6 way (6P6C) so only the centre 4 pins will be connected to the RJ10 socket in the converter. 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. Lead length is approx. 14cm.