Wikipedia
A modular connector is an electrical connector that was originally designed for use in telephone wiring, but has since been used for many other purposes. Many applications that originally used a bulkier, more expensive connector have converted to modular connectors. Probably the best known applications of modular connectors are for telephone and Ethernet.
Modular connectors were originally used in the Registration Interface system, mandated by the Federal Communications Commission (FCC) in 1976 in which they became …
Modular connector - Wikipedia, the free encyclopedia