10 Oct
2010
10 Oct
'10
10:38 a.m.
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.
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...
In particular :
What pins would I expect to find a normal 'switched' telephone line on (4
and 5, I think?)
What about a 2-wire leased line ('private circuit')? Or a 4-wire one?
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?
In case anyone's wondering, I've bought a non-working telephone line
simulator, and am trying to make sense of the numerous relays connected
to the telephone connectors, which are RJ45s (genuine RJ45s, with the
extra polarisation notch).
Books on US telcoms practicce are few and far between over here...
Thanks in advance for any help...
-tony
10 Oct
10 Oct
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
1 p.m.
Keith wrote:
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)
Well, actually the 6p2c RJ11 has only two wires for one line. The
two-line four-wire on a 6p4c is an RJ14. The three-line six-wire 6p6c
is RJ25. The four-line eight-wire on an 8p8c (similar to RJ45) is RJ61.
I *think* that Tony was originally referring to the RJ48S or RJ45S.
The pinouts are on the page I gave him before:
http://www.hvs.on.ca/telecom/technologies
Peace... Sridhar
1:30 p.m.
On 10/10/2010 1:38 PM, Tony Duell wrote:
IFrom what I've read, I am not convinced they are. They are 8P8C modular
connectors. The 'RJ' (Registers Jack) numbers specify a lot more than the
connector.
Apparently, too, the RJ45 connectore had an extra ridge on the plug and a
groove in the socket (jack) to take it. The connectors on the instrument
I am working on most certainly have this groove.
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.
Nothing at all as far as I am aware.
OK, perhaps I can give a little more infromation. This is a telephone
line simualtor instrument. It has a pair of RJ45 sockets on the front for
the 2 devices you want to connect together. The 8 contacts of each socket
are duplicated by screw terminals on the back.
One one of the PCBs inside are a large number of relays (of various
types), 9 are associated with each RJ45 connector from what I can tell.
Now since the instrument doesn't work yet, and I have no manual, I can't
be sure, but it appears from the LED labels on the front panel that this
unit can test either normal 2-wire 'switched' devices (it will simulate a
PSTN line), or 2 wire 'private' (what we would call a 'leased line' I
think) or 4-wire private connections (presumably one pair for the signal
in each direction.
My guess is that some of the relays select between these modes, and thus
it would be useful to know what I should be seeing on the various RJ45
pins in each mode.
I say 'some' of the relays, because I've already found one that simply
reverses the line 'battery' (supply voltage) polarity, and another that
seems to apply a rining voltage.
And I'll mention a couple more below.
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? 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)
Yes, I'd read that. And based on that, and some of the relay connections,
it would appear that at least one mode uses pins 4 and 5 -- the centre
pins -- only.
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.
I am not trying to get a telephone line installed... I have something
that pretends to be a telepgone line and has an RJ45 connector on the
front...
> Why would there be a resistor of about 866 ohms
connected between pins 7
> and 8?
There is one relay that seems to connect such a resistor. I think I read
somewhere that this was an obsolete standard (whcih may well have been
current when this thing was made) for high-speed modems. Perhaps the
resistor encodes some characteristic of the line.
Pins 7 and 8 are used for something else when this relay is not
connecting the resistor. Perhaps one half of the 4 wire line.
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
Yes, I've got those...
But knowing how to connect the wires is very different from knowing what
the wires might be used for...
-tony
11:52 a.m.
I think you're asking about USOC RJ45S, which has nothing to do with
network wiring. I've never seen a true one in the wild, but they
were used for data hookups, apparently.
Perhaps this will help:
http://www.suttleonline.com/pdfs/misc/USOC_Guide.pdf
and a bit more on programming resistor values:
http://www.shout.net/~wildixon/telecom/rj/68_502.html
--Chuck
12:02 p.m.
I should add that the RJ45S is an 8-position connector in the same
size as the ethernet variety RJ45, but it's keyed and so cannot be
inserted into an RJ45 ethernet socket. However an RJ45 plug *can* be
plugged into an RJ45S socket.
--Chuck
1:32 p.m.
I think you're asking about USOC RJ45S, which has nothing to do with
network wiring. I've never seen a true one in the wild, but they
were used for data hookups, apparently.
It's entirely possible that I am. I will take a look at the URL's you've
given and see if they make any sense with the relay connections I've
figured out so far...
Thanks...
-tony
Perhaps this will help:
http://www.suttleonline.com/pdfs/misc/USOC_Guide.pdf
and a bit more on programming resistor values:
http://www.shout.net/~wildixon/telecom/rj/68_502.html
--Chuck
12:01 p.m.
On 10/10/2010 10:38 AM, Tony Duell wrote:
What pins would I expect to find a normal
'switched' telephone line on (4
and 5, I think?)
Yes, the middle two.
What about a 2-wire leased line ('private
circuit')?
Also the middle two.
Or a 4-wire one?
Not sure about voice service.
For a T1 digital line, the pairs would be
1/2 and 7/8.
Why would there be a resistor of about 866 ohms
connected between pins 7
and 8?
That's to program the transmit power level of the device plugged into
the socket. Typically used on leased lines. On a real installation of
that type, the resistor value is chosen by the installer to compensate
for loop length.
Why would pins 3 anf 6 be shorted together?
I'm not sure specifically about about 3 and 6, but on some jacks there
are one or two shorting bars to preserve continuity of a loop when there
is no device plugged into the jack. This is used in RJ41X service,
typically for alarms, because the alarm system can seize the loop
(disconnect it from the downstream phones). When nothing is plugged
into the jack, the shorting bar provides loop continuity to the phones.
In case anyone's wondering, I've bought a
non-working telephone line
simulator, and am trying to make sense of the numerous relays connected
to the telephone connectors, which are RJ45s (genuine RJ45s, with the
extra polarisation notch).
Note that RJxx is a USOC (Uniform Service Ordering
Code), and defines
the type of service as well as what jack is used: 4-position,
6-position, 8-position, with or without shorting bars, how it is wired, etc.
While an RJ45 service uses an 8-position jack, an 8-position jack is not
in and of itself an RJ45, despite everyone misusing the USOC code in
that way. An 8-position jack could also be used for RJ31X service,
RJ41X, RJ48C, RJ48S, RJ48X, RJ61X, etc.
Similarly, a 6-position jack may be used by RJ11 service, RJ14 service,
or various others.
Books on US telcoms practicce are few and far between
over here...
The same seems to be true here in the US. Oh, there are plenty of
books
that will tell you how a basic POTS service works, but little beyond that.
The real info was in the "Bell System Practice" documents, which were
not available to customers, and in Bell standards, which were. After
the divestiture, the standards went to Bellcore, which is now Telcordia,
and the standards cost a LOT of money.
Eric
1:42 p.m.
On 10/10/2010 10:38 AM, Tony Duell wrote:
Ah, now that makes a lot of sense...
I appears that one signal (presumably either a 'bidrectional' one for
2-wire use or one half of the 4 wire set-up can be switched to either
pins 4,5 or 1,2. Pins 7.8 seem to be either the resistor I mentioend, or
not used, or another signal pair, I would guess at the other half of the
4-wire set-up. You don't happen to know which pair is Txand which is Rx,
do you?
What pins would I expect to find a normal
'switched' telephone line on (4
and 5, I think?)
Yes, the middle two.
What about a 2-wire leased line ('private
circuit')?
Also the middle two.
Or a 4-wire one?
Not sure about voice
service. For a T1 digital line, the pairs would be
1/2 and 7/8. Why would
there be a resistor of about 866 ohms connected between pins 7
and 8?
That's to program the transmit power level of the device plugged into
the socket. Typically used on leased lines. On a real installation of that type, the resistor value is chosen by the
installer to compensate
for loop length.
No, it's not that. There's a SPST reed realy (single form A, simple
on'off contact) that's wired to pins 3 and 6 on the RJ45. As far as I can
see those pins go nowhere else. So there must be some device that expects
a short between those pins under some circumstances.
Why would pins 3 anf 6 be shorted together?
I'm not sure specifically about about 3 and 6, but on some jacks there
are one or two shorting bars to preserve continuity of a loop when there
is no device plugged into the jack. This is used in RJ41X service,
typically for alarms, because the alarm system can seize the loop
(disconnect it from the downstream phones). When nothing is plugged
into the jack, the shorting bar provides loop continuity to the phones. In case anyone's wondering, I've bought a
non-working telephone line
simulator, and am trying to make sense of the numerous relays connected
to the telephone connectors, which are RJ45s (genuine RJ45s, with the
extra polarisation notch).
Note that RJxx is a USOC (Uniform Service Ordering
Code), and defines
the type of service as well as what jack is used: 4-position,
6-position, 8-position, with or without shorting bars, how it is wired, etc. The real info was in the "Bell System
Practice" documents, which were
not available to customers, and in Bell standards, which were. After
the divestiture, the standards went to Bellcore, which is now Telcordia,
and the standards cost a LOT of money.
Pity. While I am sure the ofifical standards would be interesting, I
doubt they would be worth the money for this...
Thanks.
-tony
2:29 p.m.
A bit more on the shorting switch on your tester.
It's called an "exclusion key switch" and is used to prevent an
attached device from connecting to the line. Take a look at page 17
ff. in the UDS 208 modem manual:
http://www.arcelect.com/208A-B_manual.PDF
Those of us old enough to remember Ma Bell's setups will recall that
this switch was a little transparent (IIRC illuminated) knob on the
desk set that one turned to enable the modem to access the phone
line.
I can see why this would be part of a tester.
--Chuck
3 p.m.
On 10 Oct 2010 at 14:29, Chuck Guzis wrote:
Those of us old enough to remember Ma Bell's
setups will recall that
this switch was a little transparent (IIRC illuminated) knob on the
desk set that one turned to enable the modem to access the phone line.
Or, on some sets, one of the switchhook buttons that was pulled
upwards.
--Chuck
11 Oct
11 Oct
1:33 p.m.
A bit more on the shorting switch on your tester.
It's called an "exclusion key switch" and is used to prevent an
attached device from connecting to the line. Take a look at page 17
ff. in the UDS 208 modem manual:
http://www.arcelect.com/208A-B_manual.PDF
Thanks. Yes, that makes a lot of sense.
As an aside, I am not sure how off-topic this instrument is. OK. it's not
a classic computer, but I intend to use it for testing classic computer
peripherals (modems, of course). It is, iteself, over 20 years old, and
while it is not user-programmable (AFAIK), it does contain _6_
microprocessors (3 off 8085, an 8049, an 8041 (display driver, that one I
can see the purpose of) and a 32C010 DSP).
-tony
10 Oct
10 Oct
12:55 p.m.
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.
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...
In particular :
What pins would I expect to find a normal 'switched' telephone line on (4
and 5, I think?)
What about a 2-wire leased line ('private circuit')? Or a 4-wire one?
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?
In case anyone's wondering, I've bought a non-working telephone line
simulator, and am trying to make sense of the numerous relays connected
to the telephone connectors, which are RJ45s (genuine RJ45s, with the
extra polarisation notch).
Books on US telcoms practicce are few and far between over here...
Thanks in advance for any help...
Try: http://www.hvs.on.ca/telecom/technologies
Peace... Sridhar
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