10 Oct
2010
10 Oct
'10
11:44 a.m.
On 10/10/2010 1:38 PM, Tony Duell wrote:
Can anyone suggest URLs, etc that give the wiring of
RJ45 sockets. in
telecom applications. Not 10bse<n> (which from what I understand are not
strictly RJ45's anyway), or ISDN, but older telecoms.
All of the recent(last 10 or 12 years) ethernet standards all use 8-wire
RJ45's. They are as strict of RJ45's as they can be. This doesn't
imply that all standards require all 8 wires, but they use 8 position
contacts, plugs, jacks, standard cabling and so on.
The web pages I've found soe far give the wiring
for up to 4 POTS lines
on an RJ45, which is, again, not what I am looking for...
What pins would I expect to find a normal 'switched' telephone line on (4
and 5, I think?)
Can you help us out what the difference is between POTS and what you are
calling normal switched telephone lines?
If you are talking about regular telephone service, as delivered in the
US over copper, then "public switched telephone network" (PSTN) is
equivalent to Plain Old Telephone Service(POTS).
The center pair of wires are normally the first tip & ring, with the
next outside pair being the second line. On an RJ11, this is
2&3(normally green & red) for the first, 1&4 for the second.(normally
black and yellow)
The telco's will normally not deliver or install an RJ-45 for regular
telephone service --- but there's no reason why they couldn't -- as long
as you used compatible cables pinned & paired properly.
What about a 2-wire leased line ('private
circuit')? Or a 4-wire one?
Well the 4-wire leased circuits I can think of are traditionally 64kbps
DDS circuits(a single DS0), or a T1.
These also use an RJ45 (although the nomenclature for telcos is usually
RJ48 with minor real technical difference and no practical differences),
1&2 and 7&8 on the DDS, and 1&2 and 4&5 on the T1.
The telcos will lease what we would call dry-pairs(or sometimes alarm
circuits) for connecting two locations together through the CO, with no
real service (outside of maintenance) on the circuit itself.
Why would there be a resistor of about 866 ohms
connected between pins 7
and 8?
Why would pins 3 anf 6 be shorted together?
I don't have an answer for this.
The EIA/TIA has standards called T568A and T568B which specify color
pair connects to which pins on the connector. T568B is normally the
networking standard, and A is normally telco standard. (these standards
switch the green and orange pairs)
http://en.wikipedia.org/wiki/T568A#T568A_and_T568B_termination
http://en.wikipedia.org/wiki/T-carrier
http://en.wikipedia.org/wiki/Pstn
Since most popular circuits (all of what you've mentioned and more) use
the same pairing(1&2, 3&6, 4&5, 7&8), once you've installed and wired
your jacks, patch panels, punch downs, cables this way ---- everything
should just work. Which signals travel over which pairs obviously
doesn't matter, outside of keeping a consistent premise cabling
standards for future A/M/C's.
Does this help?
Keith