What type of jack would you normally use for a POTS line?

What type of jack would you normally use for a POTS line?

• RJ9
• RJ31X
• RJ11
• RJ45 

 

EXPLANATION

An RJ11 jack supports one POTS (Plain Old Telephone Service) line.
An RJ9 is an unofficial 4P4C plug that is sometimes used for the handset connection to the telephone.  Think the coiled cord. (http://blog.jabra.com/4-types-of-wired-headset-connectors/)
An RJ31X is a special type of jack that can accommodate up to two POTS lines, but is wired using 4 pairs of wire.  This can be described as an intercept or "Man in the Middle" plug.  It is most commonly used with alarm systems,  When the alarm panel is plugged into the jack, the POTS lines pass through the alarm system.  This allow the alarm system to seize the line, possibly dropping a call in progress.  When the alarm system is not plugged into the jack, the POTS lines work normally.

An RJ45 is the jack most IT people are familiar with.  It is the 4 pair plug we normally associate with ethernet and patch cables.