atcomsystems.ca/forum Forums General General Telephone & Systems Information Information about the "RJ"

Many people hear the term "RJ" but have no clue what that means and they create their own interpretations. This creates a lot of confusion, but most professionals in this busines have learned how to understand what the customer "really" wants.

I thought I would share this to enlighten anyone who is not familiar. Here are some links to a relatively basic explanation:

https://www.arcelect.com/USOC_codes-Universal_Services_Ordering_Code.htm

https://www.arcelect.com/RJ_Jack_Glossary.htm

Today, there are so many "invented" RJ's, like RJ9 (supposedly for handset cords) that I couldn't resist this post. Of course, the link I attached isn't anywhere near the total list of real RJ designations. It's just a start, but it sure addresses the most popular two misnomers; RJ11 and RJ45. Take a look and you'll see what I mean. More to follow.

Ed

Good post . Maybe a future post could be on the RJ2IX and the different letters associated with that one .

Just out of curiosity, what is the correct name for the jack and the wire of the jack, that is used for alarm systems. The one you put on the front end of the pots line and has the shorting bars in it?

I think that is an RJ-31X

https://www.hometech.com/learn/rj31x.html

A quick page on how to wire in rj-31x

I knew this was comming as soon as I saw the RJ9 post. I thought ot myself (here comes Ed) LOL


Good read tho,.. very informative

Waine
The good news was it was only about a 100 words. :rofl:

We call that the CA38A jack here. Not sure where that comes from, Ed fill us in!

I know it is called a CA31A and because we tamper it to a zone on the alarm system, it becomes a CA38A. We install an EOL resistor or a short across pins 2&7 and make that zone show "trouble" on the panel if it's unplugged.

Ed you'll love this, look below to see what they say it's used with.

https://www.pacificcable.com/Picture_Page.asp?DataName=R9

Yes, it's an RJ31X for the standard tip/ring in and out. The RJ38X is identical except that the jumper is wired across pins 2 and 7 to let the alarm system know that the jack is unplugged. It's not really used much anymmore because newer alarm panels have the ability to sense voltage on the line.

You know Bill, it's just as much the manufacturer's and distributor's responsibility for dreaming up these "artificial" terms being used today.

Even they can't be consistent with there own definition, in the first part they say handset cord and the next they say it's for flat satin base cords, they need to make up their minds. I think the RJ debate will rage on, main thing is we know which wiring scheme to use for each purpose. I thought you might get a kick out of a link that contradicted its self.

Just for your info Ed,
We try not to use that feature on the newer panels. Yes it senses voltage on the line, however on a service note, it's a pain in the a$$. If the line disappears, which can happen pretty easily, someone working on the line, a line cut, moisture, etc. the siren and/or keypad starts sounding. Some panels (DSC for example) it doesn't tell you on your keypad why this type of alarm went off until you go into a deeper event buffer looking for it. As a result, a service call at 3am in the morning! The other problem is, just because you have line voltage doesn't necessarily meen you have dial tone for your alarm to call out on. If the customer needs that sort of protection (line cut) he should go to an alternative communication method eg. cellular, DVACS in Canada, long range radio in the States, etc.

By the way, where did the CA part come from?

why in the USOC (from what I have seen in catalogs) does it say that and RJ21X is for 'traffic data recording equipment'?

Twisted, I don't know about the CA but I'll bet that the C stands for Canada! We always wire these jacks as RJ38's just in case; it certainly can't hurt and then the alarm installer has the choice as to whether pins 2 and 7 are used for a trouble circuit or not.

Jeff, there is an RJ71C that's similar to the RJ21X in appearance, but it functions more like twelve RJ31's. That is, the top 12 pairs are CO lines IN and the bottom 12 pairs are CO lines OUT to the key or PBX equipment. This allowed in-line devices, like bulk toll resrictors or traffic measuring (mechanical call accounting) systems to be connected. The lines would loop in and back out of these devices when plugged into the 25 pair jack on the side of the RJ71 block.

You probably won't see too many of these anymore, but they did exist. Some of them had a feed-through plug that had to be left plugged in to keep the lines flowing in the event that the equipment had to be unplugged for service. As you can imagine, this was terribly inefficient since you had to kill all 12 lines momentarily to unplug the toll restrictor. Most companies ended up using individual RJ31X jacks instead.

I guess seeing 'traffic data recording' i was thinking of traffic like cars on a street

I was just talking to another tech here tonight and he thought that CA stood for "Call Appearance." We also call our 25 pair amphenol demarcation a CA21A. Maybe that's just a Canuck thing?!!

No, I doubt that is what it means. Isn't there a Canadian equivalent of the FCC? There must be some reference to the Canadian standard for jacks. Or is the Internet frozen up there for now?

Ed

Do you think the designation RJ21X is really RJ21X or RJ2IX ? Jeff Moss seems to be inquisitive on RJ designations . Shall we explain to him the difference between a RJ2EX and a RJ2GX . Asking questions is one of the few ways we have to gain knowledge .

Well, I just had to google this: Here's what I found:
RJ2DX: USOC RJ2DX is the Network Interface for multiple connection of up to twelve 4-wire trunks or lines. Signaling can be either loop start, ground start, or reverse battery. Provides a multiple connection of tip and ring to equipment, and utilizes a KS16690-L1 50-pin miniature (female) ribbon connector.

RJ2EX: USOC RJ2EX is the Network Interface for multiple connection of up to twelve 2-wire tie trunks with E & M type-I signaling. Provides a multiple connection of T, R, E & M leads to equipment, and utilizes a KS16690-L1 50-pin miniature (female) ribbon connector.

RJ2FX: USOC RJ2FX is the Network Interface for multiple connection of up to eight 2-wire tie trunks with E & M type-II signaling. Provides a multiple connection of T, R, E, M, SG and SB leads to equipment, and utilizes a KS16690-L1 50-pin miniature (female) ribbon connector.

RJ2GX: USOC RJ2GX is the Network Interface for multiple connection of up to eight 4-wire tie trunks with E & M type-I signaling. Provides a multiple connection of T, R, T1, R1, E & M leads to equipment, and utilizes a KS16690-L1 50-pin miniature (female) ribbon connector.

RJ2HX: USOC RJ2HX is the Network Interface for multiple connection of up to six 4-wire tie trunks with E & M type-II signaling. Provides a multiple connection of T, R, T1, R1, E, M, SG and SB leads to equipment, and utilizes a KS16690-L1 50-pin miniature (female) ribbon connector.

RJ2MB: USOC RJ2MB is the Network Interface for multiple connection of up to twelve 2-wire lines requiring a Central Office make-busy indication. When the registered equipment provides a contact closure between MB and MB1 leads, a make-busy indication is transmitted to the network equipment busying out the line from further calls. Utilizes a KS16690-L1 50-pin miniature (female) ribbon connector.

Also, what is E&M?

Sorry. Page locked and posted twice.

E&M trunks also called "tie" lines, are special trunks that tie two distant telephone systems together. They allow the users of either telephone systems access to the users and resources of the other telephone system.

BTW, E&M stands for recEive and transMit (or Ear and Mouth).

Mac

Is correct on the E receive and M transmit . In theory the local PBX would cause a change in current on it's M lead which would send a "wake up" to the distant PBX E lead . Which in turn would cause a current change in it's M lead sending a "I am ready" signal back to the local PBX E lead . Dialing registers and talk paths would be reserved in the distant PBX for the anticipated digits . When a valid dial string was entered a connection was made in the distant PBX and ringing or other sytem tones where sent back . MacGvyer can help explain why 4W E&M was preferred over 2W E&M .

"prof reader wanted"

Sure OBTW, just put me on the spot, lol. I'm actually weak on E&M but the first thing that comes to mind is that 4W is continuous signalling as I recall. I'll be Ed knows the complete answer tough :bow:

4 wire E&M was actually 6 wire at the pbx, transmit, receive and E&M. It was accomplished through simplex signaling, this was just a coil between trans and rec that used current to control the E&M as stated they were mainly used as tie lines between two PBX's. I put batt out on my M lead which grounds the E lead on the far end, then the far end gives dial tone, wink or is set for delay dial depending on the signaling scheme. Over the network it was SF, so you went your PBX to LEC to long haul simplex, long haul to far end SF than back to simplex to signal the switch. These were all individual circuits, so you can imagine what 24 of these would cost, that's why T-1's were developed, saved a ton of equipment and money for the customer. Ed here's the soap box back.

Jeff

That was very good research and posted in a very professional format . Forget the ribbon cable though . Well done in my opinion . Off subject , still fighting daulty keboard trouble .

You guys are killing me. I am not old enough to be answering these questions, but here's the answer (I think):

2 wire E&M provided a bi-directional talk path but it didn't work well over long distances. The E&M leads were still a separate pair, so technically it was still a four-wire circuit.

4 wire E&M used separate transmit and receive pairs plus the E&M leads, thus actually a "six wire circuit". Separating the transmit and receive talk paths greatly improved distance capabilities.

Of course, today this is not a problem because now they are just emulated using digital circuits.

Man, I hope I am at least close in my answers here.

justbill

Sounds like you spent alot time on the CO end. SF,long haul ,simplex . What was your CO duties?

Private line remote testing mostly in my later years. Put a lot of E&M circuits in on Dimensions. We also had test jacks between us and LEC when divestiture first happened so you got to mess with a lot of that stuff. After a while it all became testing from a computer terminal.

Where you offered or did you take the " Golden Handshake " ? A lot of the tech's I know in Calif did after divestiture . I am fighting the computer terminal trouble shooting tester syndrome myself . I like going into the "trenches" but my knees don't .

you got it just bill, remote access to all test points, remote access to pots lines test, remoate access to switch terminals. even remote access to some channel banks on customers sites. Really cut down on the amount of field techs who actually know what they are doing, and the now you get guys testing ckts who have never seen a smart jack never mind a CO

Bill it looks like we have a similar background from the 1970's. I still have a MAAP panel for the Dimension 400's and one for the 2000's

This tread takes me back to my C.O. days in the TOLL and XBT offices.

Haven't seen a MAAP in many years, haven't seen the CSU or SAU for the horizons either, of course even RMATS remoted the Dimensions later.

Anthony, I took a buy out in 2001. The first day I walked into a test center in 85 and saw all those people sitting behind computer terminals I came very close to quitting. I got use to it after awhile, what got me is they'd put people in there who had never wired or actually worked on the circuits or the PBX's and they would be testing. I never could figure out how you could test and know how to fix something when you really had no idea how it really worked, and unfortunately most didn't. The ones that could I had a lot of respect for. When I retired unless you actually needed a CO tech to change a pack or something everything was done remotely. Ahhh memories.

EV asks: Isn't there a Canadian equivalent of the FCC?

No, Canadians don't put their heads up their asses.

MacGyver says: Sorry. Page locked and posted twice.

I'm not with NSA any longer, what does this mean?