Modular connector, electrical connectors originally used in telephone wiring, now is used for many other purposes. Probably the most well known applications of modular connectors are for Phone Jacks and for Ethernet jacks in Ethernet Cabling, both of which are nearly always modular connectors.
Modular connectors also called Telephone Modular Jack, RJ connector (RJ stands for Registered Jack- a physical connector interface most often used for telephone wire terminals), and Western jack/plug. The term “modular connector” arose from its original use in a novel system of cabling designed to make telephone equipment more modular. This includes the 4P4C handset connector which is sometimes called an “RJ9″ or an “RJ22″ — but such RJ specifications are absent in the current FCC documents. 8P8C modular connector type is often called RJ45 plug, and RJ45 plugs are also used with different signals, such as for Ethernet over twisted pair. RJ11 is the most familiar of the registered jacks, due to the fact that virtually all single line telephone jacks in most homes and offices use this connector type.
Modular jacks are defined as “male” or “female”, depending on if they will be inserted or if a component will be inserted into them. Male connectors are called plugs, while female connectors are called jacks or sometimes sockets. Plugs are used to terminate loose cables and cords, while jacks are used for fixed locations on surfaces such as walls, panels and on equipment. Phone jacks and plugs have very similar packaging even though the functions that they perform are not similar at all. Modular jacks come in a wide range of different types from modular connectors and plugs, phone jacks, computer and Ethernet jacks, to Internet connections and electronic components.
Another very common type of modular jack is that of the telephone or Ethernet jack. This small unit is connected to a telephone cord which then transmits a telephone analog signal from a special phone outlet placed on a wall, desk or cubicle to the actual phone unit. If the telephone jack becomes loose or is removed from the telephone outlet for any reason, the signal is lost and phone calls cannot be made. Telephone jacks are generally small square plastic attachments which contain tiny wires inside as well as a release tab.
A third type of modular jack belongs to the personal computer that can be connected to a local or worldwide network, such as the Internet. While older desktop computers or those connecting to an internal network can connect via a telephone jack sending a signal down telephone lines facilitated by the use of a dialing modem, many computers use cable or digital signals to connect to the Internet. In some cases, the signal can also be sent wirelessly through a router, which is connected to this modular jack with a special cable.
Modular jacks are in wide use in many buildings around the globe due to their ease of use. They are an inexpensive alternative to direct wiring of electronic devices. In many buildings, the most common form of modular jack is the electrical connection, cord, or plug. Outlets which provide electricity to electrical-powered devices connect them via a wire or cord that hooks together in a special modular ending, such as a set of metal prongs found on the average electrical cord. Once the prongs are inserted correctly into the associated outlet, electrical power is transferred from the outlet to the device and it is ready for use. The modular jack must correspond with the outlet in order for this power exchange to take place.