What is RJ Telephone Plug and Socket System?

RJ stands for Registered Jack. The RJ standard is currently the most popular standard for telephone connection interface in the world, and has been adopted in many countries, such as Canada, China, Japan, Singapore and the USA, etc.

RJ Socket	RJ Plug
RJ Socket	RJ Plug

Implementation of the RJ Standard in Hong Kong

• In consultation with the telecommunications industry, the Communications Authority (CA) has decided to adopt the RJ standard as the plug and socket standard in Hong Kong for connecting telephones and facsimile machines* to the public switched telephone networks (PSTNs). The RJ plug and socket system gradually replaces the BT system.
• The telecommunications industry has prepared for the transition from the BT standard to the RJ standard. Fixed telecommunications network service (FTNS) providers have already installed RJ sockets for some of their customers.
• All FTNS providers install RJ sockets for their customers in new installation, relocation or maintenance projects.
• The RJ and BT systems will coexist in Hong Kong over a period of time. CA encourages telephone and facsimile machines* suppliers to provide appropriate BT-RJ adaptors or plug convertors to their customers during this transitional period.