The RJ-11 (registered jack-11) plug is the most common type of plug wiring.  You will find them in your households or office phones which are plugged into an ordinary "untwisted" wire.  An RJ-11 socket has 6 pairs of wires on the terminal, it has colors indicated on the terminal, and normally 4 wires are used.  The 4 wires are usually distinguish in black, white, red and green.  The black and white wires are normally used for low-voltage signal such as phone lights.  The red and green wires are primarily use for carrying voice or data transmission.  Besides finding RJ-11 in your typical house phones, you can also find RJ-11 in your PC modems.

• Up to six (6) pins
• Width of the plastic housing is approximately 3/8 inch
• Commonly used in telephone modular cords between the wall and telephone

RJ- 45 Plug Wiring

The RJ-45 (registered jack 45) plug is similar in shape and appearance to RJ-11, but with a much wider housing since it contains eight wire connectors.  The purpose of this design is to increase a higher data transfer rate.  The RJ-45 is commonly used to connect computers onto local-area network (LAN), especially Ethernet "10-Base T" and "100-Base T" network cabling.  For example, between the patch panels wiring closet and workstation for equipment such as file servers.

• Up to eight (8) pins
• Width of the plastic housing is approximately 11/32 inch
• Commonly used in "10-Base T" and "100-Base T" network cabling, Star DP8340Rx series serial data cables also use this connector.