Telephone Plug and Socket System in New Look

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

• Most of the customer premises equipment (CPE) available in the world market (including telephones and facsimile machines) has adopted the RJ standard.
• RJ plug and socket system can support voice and data services. It is well-recognised that the RJ system is superior to its counterparts.

Implementation of the RJ Standard in Hong Kong

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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.

Tips to Consumers

• CA recommends consumers to purchase telephones and facsimile machines* equipped with RJ plugs.
• When relocated to new premises, or when new telephones and facsimile machines* equipped with RJ plugs are purchased, consumers may encounter incompatible RJ/BT plugs/sockets. Under most circumstances, such connection problems can be resolved by using BT-RJ adaptors or telephone cords with the right plugs.
• Sometimes maintenance works carried out by FTNS providers involve change of sockets. Customers may come across difficulties in matching the facsimile machines* with newly installed RJ sockets. Under normal circumstances, service providers are willing to help customers resolve the connection problems.

* and other customer premises equipment (CPE), such as modem

For more information, contact us at:

Telephone : 2961 6636
Fax : 2838 5004
Email : standards@ofca.gov.hk