Modular Jacks(connector)

Modular connector is the name given to a family of electrical connectors examples of which are pictured. These connectors were originally used in telephone wiring. Even though they are still used for that purpose they are used for a variety of other things as well. A modular connector's advantage over many other kinds include small size and ease of plugging and unplugging. However the plastic retaining spring clip tends to get broken off when cables are pulled from storage for use. If that happens, the plug can easily fall out of the wall jack. Many uses that originally used a bulkier connector have migrated to modular connectors. Probably the most well known applications of modular connectors is for telephone jacks and for Ethernet jacks, which are nearly always modular connectors.

Modular connectors were first used in the Registered Jack system, so Registered Jack specifications describe them precisely. Those are the specifications to which all practical modular connectors are built. However, the Registered Jack specifications name the wiring patterns of the jacks, not the physical connectors of either sex. Instead, these are covered by ISO standard 8877, first used in ISDN systems.