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TIA-568A and RJ-45 inconsistency
Please see Talk:TIA-568A#TIA-568A and RJ-45 inconsistency.
Rafał Pocztarski 07:34, 30 Jul 2004 (UTC)
Question about RJ-11 and RJ-45
- Does RJ-45 allow connections to the RJ-11 Landline Telephone network? —Preceding unsigned comment added by 126.96.36.199 (talk • contribs) 01:48, 3 August 2004 (UTC)
Which way? What do you mean? You can insert a telephone plug into an RJ-45 socket and if the 1st (white/blue) pair (two central pins) of RJ-45 socket is connected to a telephone line (which does not interfere with Ethernet which uses only the 2nd and 3rd pair), then your one-line phone will work just fine. Smaller plugs can be inserted into larger sockets. Is that what you ask for? Rafał Pocztarski 06:30, 3 Aug 2004 (UTC)
- I worked at a computer shop where they had a couple of their RJ-45 sockets wired up to the phone line, and then RJ-11 to RJ-45 adapters in them so you could just plug a phone cable into it, very convenient when you need to test a modem and the main phone socket's behind a heavy unit. —Preceding unsigned comment added by Boffy b (talk • contribs) 10:48, 30 September 2004 (UTC)
It is actually possible to do both at the same time although you may think twice about this as it is (AFAIK) not formally approved due to the dangerous voltages that can occur on a telephone line. You wil find in most hubs and switches that the centre blue pair is normally shortened for reduction of cross talk, so you'll have to patch in the plug or get creative. RS Components in the UK do a socket that takes such a single cable and splices it back out into a network socket and a telephone socket, but beware of the color code they use as it is not Krone standard (took me a while to sort out why things didn't work as they should ;-).
Why do people insist on calling modular connectors RJ-xx before wiring them?
The RJ-xx designation defines a specific connector, AND a specific wiring pattern, for a specific application. The various connectors used for telecom and data applications DO NOT have any RJ-xx designations by themselves, and only gain a RJ designation when a particular connector is wired to a specific wiring pattern, for a specific telecom application, as defined in the applicable USOC. The RJ-xx designations were originally specified in 47 USC 68.502, and are now managed by a telecom industry working group.
This should be obvious, given that the same connectors are used for multiple (and frequently incompatible) RJ-xx applications. For instance, the unkeyed 8 position 8 contact (8p8c) modular connector is used for RJ61, RJ31,RJ32, RJ33, RJ34, RJ35, RJ36, RJ37, RJ38, Ethernet, etc, all of which have different wiring patterns.
The connector that is specified for RJ-45 is actually a KEYED 8p8c connector, (also specified for RJ41, RJ42, RJ43, RJ46, RJ47, and certain versions of RJ48). The keyed plug will not fit into an unkeyed jack, although the unkeyed plug will fit into a keyed jack. RJ45 also specifies a wiring pattern that has no connections in common with 10baseT or 100baseTX ethernet.
Other examples would be RJ11, RJ12, RJ14, RJ25, where RJ12 and RJ14 are incompatible, and a device wired for RJ12 will short out the second line on a jack wired for RJ14.
It's also worth mentioning that not all RJ-xx applications use a modular connector, in particular, RJ-21, and some versions of RJ48 use a 50 position ribbon connector (frequently, and probably incorrectly) referred to as an "Amphenol" connector. This is the same connector that was used on the old 1A2 key telephone systems that were common up until the 1980's.