Registered Jack 11 or simply R-J11 is a connection interface or connector used to plug cables with the wall outlet. In general, RJ-11 is also named as modem port, phone connector, phone jack or phone line in a nontechnical way.
RJ-11 Wiring 2 or 4 Pins
There are male and female RJ-11. RJ-11 has 6 connector positions but in general 2 or 4 of them are used in practice. Generally untwisted and unshielded twisted pair (UTP) cables are used to end with RJ-11 connector. We can see below that RJ-11 is implemented as 4 connecting cables with 4 pins.

In the following example, only two pins are used and other pinholes are not used for a cable connection.

6 pins can be used in rate situations for telephones. 6 pins RJ-11 can be used to connect 3 phones to the telephone line.

RJ-11 Types
There are two types where C type is used for desktop phone jack with the name RJ-11C and W type which is used for wall-mounted jack with the name RJ-11W.
RJ-11 Use Cases
RJ-11 is a popular connector type like RJ-45 where it can be used for different cases. Here are some of them.
- `Phone` is the most popular use case for RJ-11. Phones are connected to the wall outlets with RJ-11 connectors.
- `Modem` is another use case which is related to the phone. Modems are using the phone line where it uses RJ-11 connectors. In the old days, computers and the notebooks have RJ-11 for a modem connection.
RJ-11 vs RJ-45
RJ-45
is another popular connector type. Generally, RJ-11 and RJ-45 are compared with each other. In this part, we will compare both connector types with each other.
- The RJ-11is used for telephone lines where RJ-45 is used for computer network
- The RJ-11 has 4 wires in general and 6 wires at max where RJ-45 has 8 wires
- The RJ-11 connector is smaller then RJ-45 connectors
- The RJ-11 connector can be plugged into a RJ-45 slot but it will not work and may damage the devices
RJ-11 vs RJ-12
Well, actually RJ-11 and RJ-12 are very same connectors where only the cable and pin count is different. RJ-12 uses 6Pin 6 Cable which means all 6 pins are used by the 6 cables. Both RJ-11 and RJ-12 are used for telephone lines.
- RJ-11 has the same six-slot connector and size as the RJ-12
- RJ-11 differs from RJ-12 in cabling where RJ-11 has 4 cables but RJ-12 has 6 cables
- Both RJ-11 and RJ-12 used in the same cases as phone
- RJ-11 is commonly used in homes and offices where RJ-12 is very low usage which is in large companies