Electronics > Beginners

LAN Connectors (terminology)

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metrologist:
What is the proper term for the ethernet connector on your PC or laptop? Are these always referred to the same? I read some info that makes me wonder if the wiring to the PCB is always the same or could be different? Say if one instrument says it is an RJ45 connector vs and RJ48C connector (and I think the RJ spec just talks about the cable wiring).

For an Ethernet connection, is it wrong to call it an RJ48C connector?


--- Quote ---The RJ45 specified a data jack with the dialtone connected to pins 4,5. In
no other application can an 8 pin plug/jack be correctly called "RJ45",
even though just about everyone does. 8-)

Even the RJ48 series has variations. The RJ48C is the most common demark
for T-1's and is wired on pins 1,2 and 4,5. The RJ48S is commonly used to
demark lower rate circuits (like 64K and under DDS circuits and the like).
It is wired on pins 1,2 and 7,8.

Ethernet 10BaseT LAN wiring uses an 8 pin plug/jack and the signals are
carried on pins 1,2 and 3,6.
--- End quote ---

tooki:
Yes, that’d be wrong, too. (RJ45 for Ethernet is technically wrong, too.) It’s properly an “8P8C modular connector”, with the wiring being either T568B or T568A (same pinout on both ends of a cable for straight through, one end of each pinout for crossover). T568B is by far the dominant type, so that’s what I follow when terminating Ethernet cables. And then there’s the Category rating of the cables and connectors themselves, which specifies performance (and in the cables, the pair twisting).

In practice, calling it an Ethernet connector is usually sufficient, especially since many of the jacks on Ethernet endpoints (routers, switches, computers, etc) contain the Ethernet transformer right inside the jack, making it a special jack exclusively usable on Ethernet.

metrologist:
Well, it's confusing still because  have this idea that RJ45 is was the old standard - how my 40 year old phone was wired to pins 4,5.

Then we have Ethernet and it is not wired to pins 4,5. I guess that is different than the WAN port, which is wired to pins 4,5? It must because that WAN is on my old phone line in the walls.

tooki:
Huh?

Few people have actual RJ45 (8P8C) phone jacks at home. They are usually RJ11 (6P2C for a single line), RJ14 (6P4C for two lines) or rarely RJ25 (6P6C for three lines).

None of the above has much relevance to Ethernet. (Though pins 4 and 5 most definitely are used, they’re Pair 1, which is why an Ethernet wall socket can be pressed into service for POTS use.)

WAN vs LAN has no relevance. That’s a logical (data-level) distinction, not one of wiring.

Please review the T568B wiring standard.

And maybe you can clarify what it is you’re trying to learn — cuz it seems to me it wasn’t just the names of the connectors.

Nusa:
The RJ (Registered Jack) standards were established as standard network interfaces between customer equipment and carrier equipment. The RJ number specifies both the physical connector and how it is wired. Ergo, if your modular jack/connector isn't intended to connect to the outside world, it technically is not an RJ connector/jack, even if it uses exactly the same modular connector.

RJ48 is 8p8c used for modem connections like ISDN, T1, and others.
RJ48C is an RJ48 specifically wired for a T1 circuit using pins 1,2,4,5

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