Telephone connection cable

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RJ11 plug with 4 contacts for a telephone connection
TAE plug type F for Germany
Telephone plug in Switzerland

A telephone connection cable connects a telephone with the "telephone socket" (TAE socket) . Corresponding cables are also available for other telecommunication devices such as answering machines , modems or fax machines .

In principle, only two wires are required for telephones. For the simultaneous operation of several devices on one connection, however, several wires can be useful or even necessary. The TAE socket therefore offers six contacts.


In Germany, the cable usually connects a TAE plug and an RJ-11 plug. The RJ plug is plugged into the analog telephone when the cable is not firmly connected to the telephone (or other device). For ISDN , RJ plug connections (RJ-45) are usually used on both sides, and very rarely a TAE plug on the socket side. In Switzerland, the cable connects a Reichle plug (mostly TT89 assignment 1a and 1b) with an RJ11 plug. The TST plug used in Austria looks very similar to the TAE system, but it is an independent standard with up to 10 plug contacts. The TST connector is used universally, both for analog (POTS) and ISDN (the NTBA is connected to the TST socket with a cable) and for unbundled lines.

Occupancy analog telephone

meaning TAE-F connector RJ11 connector RJ11 connector

(foreign phones)


( a / b interface )

1 5 3
b-core 2 2 4th
a-wire for second alarm clock ( second ringing device ),

not used today

3 4th 5
Earth for outside line access of the extension and DEV ,

not used today

4th 3 2

Occupancy ISDN

Pin / screw terminal of the UAE junction box Telephone connector assignment (TAE-F connector assignment) Western connector assignment (KJ11 connector assignment)

1 1a / red
2 1b / black
3 2a / white 2a / white
4th 2b / yellow 1a / red
5 1b / black
6th 1b / yellow

The abbreviation "UAE" stands for universal connection unit.

See also

Web links