RJ11 connector and telephone interface detailed introduction

RJ11 connector and telephone interface detailed introduction

When you mention RJ11, you know that it is a universal telephone connector. In fact, it was originally a generic name for a connector developed by Western Electric Company in the United States. It was originally named WExW and has a 6-pin shape. WE6W uses all 6 contacts, while WE2W only uses the middle two pins. Later, it became one of the RJ series connectors.
The name RJ stands for Registered Jack, which comes from the USOC (Universal Service Ordering Codes) code of the Bell System. USOC is a series of registered jacks and their wiring methods developed by the Bell System to connect users' equipment to the public network, and is now specified by FCC documents.

RJ11, RJ14 and RJ25 are in the same series and have the same size, all 9.5mm wide, but with different number of contacts. RJ11 has only one pair of contacts in the middle, which can connect one pair of wires, expressed as 6P2C (six position, two conductor); RJ14 uses four contacts in the middle, which can connect two pairs of wires, expressed as 6P4C; RJ25 uses all six contacts, which can connect three pairs of wires, expressed as 6P6C.

The following is the line sequence and color table of this series:

RJ11 is also used as an RS-232 or 485 interface. Here are three examples:

Sometimes this connector can also be used to provide low voltage and low power (AC or DC), and PIN2 and PIN5 (black and yellow wires) are commonly used.
RJ11 is generally used as a general term for this 9.5mm series, and RJ11-6P2C, RJ11-6P4C and RJ11-6P6C are used to distinguish the number of contacts.

The phone also uses a connector to connect the phone and the handle, called 4P4C (some people also call it RJ22, and it forms a series with RJ9 and RJ10). It has 4 contacts and is 7.5mm wide, which is smaller than RJ11. The wiring method of MIC and headset is shown in the figure below:

This connector is also used in Apple's Macintosh to connect the host and keyboard, and DirecTV set-top boxes also use this connector.

RJ11 is the American standard telephone connector, while the UK is BS 6312, France is F-010, and Germany is TAE connector, which are basically similar, while Austria is TDO-connector and Poland is WT-4, which are very different.

The more commonly used RJ connector is RJ45, which is used for Ethernet connection, 8P8C, can connect 4 pairs of twisted pairs, 12mm wide, wider than the RJ11 series. RJ45 is sometimes also used for telephone or RS232 connection, and some people use it to transmit VGA video signals.

There is also an 8P8C connector called RJ61, which is used to connect twisted pairs. The line sequence is as follows:

Because the two wires in the 3rd and 4th pairs of twisted pairs in this line sequence are far apart, it will cause greater crosstalk and is not suitable for the transmission of high-frequency signals such as Ethernet.
There is also an RJ48 connector, which is also 8P8C, which can be used to connect 4 pairs of T1 data links. Each pair of wires can transmit 23 time-division multiplexed voice channels.

Other less commonly used RJ series connectors include:
RJ2MB: 50-pin miniature ribbon connector
RJ12C/RJ12W: 6P6C, for one telephone line ahead of the key system RJ13C/RJ13W: 6P4C, for one telephone line behind the key system RJ15C : 3-pin weatherproof, for one telephone line RJ18C/RJ18W : 6P6C, for one telephone line with make-busy arrangement RJ21X: 50-pin miniature ribbon connector, for up to 25 lines RJ26X: 50-pin miniature ribbon connector, for multiple data lines RJ27X: 50-pin miniature ribbon connector, for multiple data lines RJ31X: 8P8C (usually only 4C are used), single line with alarm - center pins #4 & #5 connect to phone line; outside pins #1 & #8 connect to another phone jack allowing the alarm dialer or medical alert system to dial the monitoring company when triggered. RJ38X: 8P8C, similar to RJ31 but a connection between pin #2 & #7 indicates that a plug is inserted. RJ41S: 8P8C keyed, for one data line, universal RJ45S: 8P2C + keyed, for one data line with programming resistor RJ49C: 8P8C, for ISDN BRI via NT1 RJ50: 10P10C, same size as RJ45 but with ten contacts Business phone RJ71C: 12 line series connection using 50 pin connector