•Modular connectors are often referred to as modular phone jack and plug, RJ connector, and Western jack and plug. The term modular connector arose from its original use in modular wiring components of telephone equipment by the Western Electric Company in the 1960s. This includes the 6P2C used for telephone line connections and 4P4C used for handset connectors.Registered jack designations describe the signals and wiring used for voice and data communication at customer-facing interfaces of the public switched telephone network. It is common to use a registered jack number to refer to the physical connector itself; for instance, the 8P8C modular connector type is often inaccurately labeled RJ45 because the registered jack standard of that name specified 8P8C modular connectors. A common use of 8P8C connectors is Ethernet over twisted pair. Likewise, the 4P4C connector is sometimes erroneously called RJ9 or RJ22—no such official designations exist—and various six-position modular connectors may be incorrectly called RJ11.