RJ-11
RJ stands for “Registered Jack”, RJ-11 is the standard connector utilized on 2-pair (4-wire) telephone wiring. The RJ-11 connector has a total of 6 connector positions, but only 2 or 4 are actually used. RJ-11 wiring comes in two standard varieties: untwisted (flat-satin cable) and Unshielded Twisted Pair (UTP).
RJ11 is the most familiar of the registered jacks, virtually all single line (POTS) telephone jacks in houses and offices in North America and many other countries use this type of connector.
Other Registered Jacks are RJ14 (a 2-line jack), RJ25 (a 3-line jack), and RJ61 (a 4-line jack), all of them use 6-position modular connectors.
An RJ11 jack is a 6P4C jack (6-position, 4-conductor), leaving two of the four wires running to the junction box unused. The extra wires can be used for a many applications, such as preventing a pulse-dial telephone from ringing the extension phone bells, as a ground for selective ringers, powering an L.E.D. ring-indicator, etc.
In a powered-up state, Pins #5 (yellow- old color code/orange- new color code) and #2 (black- old color code/white with orange stripe- new color code) carry either low voltage AC or DC power. The telephone line supplies the power for most phone terminals.
Some old telephone terminals contain incandescent lights in them and need more energy than the telephone line supplies, as their dial lights need 6.3 volts and the typical transformer output is 5 volts.
Depending on the color code convention of your wire (read left to right, while holding the jack facing you, with contacts pointing upward) the positive and negative terminals are:
Pin #3- Negative terminal (red- old color code/blue- new color code)
Pin #4- Positive terminal (green- old color code/white with blue stripe- new color code)
