Modular connectors and RJ connectors are used to connect or terminate cables in telecommunications applications. They often include thermal or electrical insulation and an integral filter that provides protection from electromagnetic interference (EMI), radio frequency interference (RFI), and electrostatic discharge (ESD). The term “modular” is used to distinguish newer, six-pin plugs and jacks from older, four-wire telephone connectors. RJ is an acronym for registered jack, a term for electrical connector designs that are registered with the U.S. Federal Communications Commission (FCC). There are several common types of RJ designs. RJ-11 connectors are six-wire devices that are used primarily to connect modern telephone equipment. RJ-45 connectors are eight-wire devices that are used most often used in 10Base-T and 100Base-TX Ethernet connections in local area networks (LAN). RJ-45 connectors are similar in appearance to RJ-11 connectors, but somewhat wider. Other common RJ connectors include RJ-25, RJ-48, and RJ-61. Specialized or proprietary telecommunications, data, and network connectors are also available.  

Modular connectors and RJ connectors vary in terms of gender, contact plating, housing, and terminal options. Male connectors or plugs contain a row of contacts and are inserted into female connectors or jacks. Connector contacts are made of metal and plated with a thin, metallic coating that improves conductivity and prevents rust and corrosion. Common plating materials include gold, copper, nickel, and silver. Contacts are usually housed in a termination assembly that is usually made of metal or plastic. There are two basic terminal options for modular connectors and RJ connectors. Through hole technology (THT) mounts components on a printed circuit board (PCB) by inserting component leads through holes in the board and then soldering. By contrast, pin termination mounts components on PCBs without soldering.    

Modular connectors and RJ connectors are used to connect or terminate cables in telecommunications applications. They often include thermal or electrical insulation and an integral filter that provides protection from electromagnetic interference (EMI), radio frequency interference (RFI), and electrostatic discharge (ESD). The term “modular” is used to distinguish newer, six-pin plugs and jacks from older, four-wire telephone connectors. RJ is an acronym for registered jack, a term for electrical connector designs that are registered with the U.S. Federal Communications Commission (FCC). There are several common types of RJ designs. RJ-11 connectors are six-wire devices that are used primarily to connect modern telephone equipment. RJ-45 connectors are eight-wire devices that are used most often used in 10Base-T and 100Base-TX Ethernet connections in local area networks (LAN). RJ-45 connectors are similar in appearance to RJ-11 connectors, but somewhat wider. Other common RJ connectors include RJ-25, RJ-48, and RJ-61. Specialized or proprietary telecommunications, data, and network connectors are also available.  

Modular connectors and RJ connectors vary in terms of gender, contact plating, housing, and terminal options. Male connectors or plugs contain a row of contacts and are inserted into female connectors or jacks. Connector contacts are made of metal and plated with a thin, metallic coating that improves conductivity and prevents rust and corrosion. Common plating materials include gold, copper, nickel, and silver. Contacts are usually housed in a termination assembly that is usually made of metal or plastic. There are two basic terminal options for modular connectors and RJ connectors. Through hole technology (THT) mounts components on a printed circuit board (PCB) by inserting component leads through holes in the board and then soldering. By contrast, pin termination mounts components on PCBs without soldering.    

Performance specifications for modular connectors and RJ connectors include number of contacts, voltage rating, current rating, conductor size, and operating temperature. The voltage rating is the maximum operating voltage. The current rating is the maximum recommended continuous flow of electrical current. Contact size or termination size is the maximum diameter wire that connectors can accommodate. In the United States, American wire gauge (AWG) is a common standard for non-ferrous wire conductor sizes. The term "gauge" refers to the wire's diameter. The higher the gauge number, the smaller the diameter and the thinner the wire. Thicker wire carries more current because it has less electrical resistance over a given length. Typical household wiring is AWG 12 or 14. Telephone wire is usually AWG 22, 24, or 26. 

Modular connectors and RJ connectors meet the requirements of a variety of national and international standards and approval organizations. Examples include Underwriters Laboratories (UL), the National Electrical Manufacturers’ Association (NEMA), and the International Electrotechnical Commission (IEC).  TÜV Rheinland/Berlin-Brandenburg provides international approval services for product safety. The CSA mark indicates compliance with Canadian standards, while the CEE and VDE marks identify conformity with European guidelines. Modular connectors and RJ connectors are also available that meet Japanese industrial standards (JIS).