Phone wiring question: RJ11 to RJ45

[Bob Vaughan]

The RJxx designations are known as a Universal Service Ordering Code (USOC), and the wiring for specific telephone services was defined in 68.502, along with the associated USOC. The specification includes the type of jack/plug, wiring pattern, and signaling.

There is no USOC for ethernet or token ring.

The connectors are obviously used for multiple uses, only some of which have USOC's, and since the same connectors are used for multiple USOC's, the connectors themselves do not have a USOC until they are wired for a specific application.

The specification for the RJ45 USOC is for a keyed 8 position/8 contact modular jack/plug, wired for a single line, bridged tip/ring, wired on ping 4/5 of the jack/plug, with a programming resistor wired across pins

7/8 or the wall jack, with a value determined based on loop loss between the jack and the CO. This allows the connected equipment to set transmit levels to not exceed -12dBm at the CO.

For comparison, 10/100 ethernet uses an unkeyed 8p8c jack/plug, wired with one pair across ping 1/2, and the second across 3/6.

Note the lack of any cross-compatibility between RJ45 and 10/100 ethernet. If properly wired, using the proper connectors, and 2 pair cable, a cable wired for RJ-45 will not fit into an ethernet jack, nor will there be any electrical continuity on any of the wires used by ethernet.

The unkeyed 8p8c jack/plug are also used for RJ-31, RJ-38, RJ-61, and others, and the keyed 8p8c jack/plug is used for RJ-41, RJ-45, RJ-48, etc.

[Reed]

The confirmed number of people in the known universe who are offended at the LAN world's usurpation of the RJ-XX terminology now stands at 2. Me and Bob.

Keep up the good fight Bob. We shall overcome someday.

Now, about the word "modem"; but ... that's another fight for another day

--Reed (old modem jockey)

[David Nebenzahl]

Reed spake thus:

So, I'm curious: does a modem to you mean a big box with a cable coming out of it that has a cradle for a telephone receiver? I remember those from my school daze ...

[Reed]

I think you are describing an "acoustic coupler". Not the same as a modem. A modem used an A/C to "couple" it's signal to a standard telephone handset, without being hard-wired.

[Jim Redelfs]

So, without running Cat5 wire, a secure WIRELESS network would probably be noticably faster than a wired one running on the old Bell 6-pr, right?

[Jim Redelfs]

Hehehehehe! Thank-you, Geordi!

[Eric]

How many angels can dance on the head of a pin? , in the day to day residential world this is the way its done RJ-11 for telephone and RJ-45 for ethernet. Eric

[Mark Lloyd]

The first modem I used was one of those "handset-coupled" things, operating at 300 baud.

[Mark Lloyd]

A modem is a mo and a dem in the same package, considering the fact that phone lines won't handle TTL levels.

[Mark Lloyd]

x=1/0 :-)

I remember someone saying they ought to be called 6P4C and 8P8C (and RJ12 is 6P6C, what is 4P4C or 10P10C?). That describes the specific connectors, but sounds awkward.

[Mark Lloyd]

Maybe not if the wired network used 10mbps equipment.

[Bob Vaughan]

Actually, RJ-12 only uses 4 conductors, and can use a 6p4c, as can RJ-13, and RJ-14. RJ-25 uses 3 pairs, and requires a 6p6c.

[mm]

OK, I know the 4c or 6c is the max number of wires, but what does 6p mean, and what does Mark refer to wrt 4P and 10P?

[Bob Vaughan]

Position (maximum number of contact positions) Contact (actual number of positions available to be wired)

A 6p4c is a plug sized for a maximum of 6 wiring positions, but with only 4 of them having physical contacts. Frequently sized so that a maximum of 4 conductor cable will fit in the plug.

You normally only see the mismatched numbering in the 6 position plugs. You can get them as 6p2c, 6p4c, and 6p6c.

[Pop`ö]

Everyone seems to have forgotten though that "RJ" defines a lot more than the number of positions and number of wires; it also defines the intended use of the plugs and receptacles and which pins are used for what. Specific examples: RJ-11, RJ31, etc. RJ-11 uses only the two center conductors for analog services, RJ-31 actually breaks a phone connection and allows one piece of equipment exclusive use of the telco pair, etc.. There are many RJ designations.

[Mark Lloyd]

I think I've seen a 4P2C once.

[markharris2000]

Old Bell 6-wire cable will not make you happy at higher data-rates (i.e. 100Mb) even if you re-crimp the shells properly (1&2, 3&6 twisted) because the old bell wire simply doesn't have the required number of twists per foot to reliably move data at high rates. I am surprised that 10Mb even worked for some folks. Perhaps shorter distances.

Anyway, 11G wireless is certainly an alternative, but again, distances and data rates are tied closely. Even great wireless 11G stuff (54Mbps) tails off in performance as the signal decreases, and at 100 feet or more, you'll probably see LESS datarate than a wired 10Mb pipe in a typical home.

Lastly, in a wired scenerio, the link make activate, but due to poor cabling, the error rate may be high, and the effective performance will be much lower. You'll need to look at error and re-transmit rates to see if you have a good solution.

Mark

Jim Redelfs wrote:

[WandaW]

replying to CraigT, WandaW wrote: Most NIDs have a provision that allows the homeowner to unplug the phone network from the house wiring.