I agree with C-H. RJ-11 already has become some kinda standard. Austrian (and german as well) phone sockets support three plugs, so you don'T have to daisy-chain appliances like for example first you have the answering machine, then the phone. You just plug the phone in the center jack and the answering machine into the right one. Only downside: Some cheap phones and modems don't support this and just block off the other devices. A nice thing that used to be supplied by our PO were the phone cords up to 10m, with extension cords up to 15m available-no more need for cordless phones. BTW: did you know that a certain model of old US cordless phone could be overheard with a standard FM radio?
Re: A common telephone connector#135141 12/21/0208:43 PM12/21/0208:43 PM
I am ashamed to say that the USA is the one that started with the foolish RJ-11 plug/socket system.
Before the RJ-11 system we had a 4-pin jack (with one pair of pins spaced slightly wider than the second). These were little cubes measuring 1.5 inches on each side...so not exactly compact. But they were robust. They very rarely broke.
The benefit of the RJ-11 is that it's compact enough for jack panels...like behind a computer on a modem, a patch panel, etc. Also once it "clicks" into place, it stays there and doesn't fall out (unlike the 4-pin plug which can slip out)
But for a household extension where you may have sockets in each room and may move the unit from the kitchen to the bedroom it is not very good. The little locking tabs break off or become weak. And once this happens, the plug is useless. Either replace the entire cord or buy a crimper tool to snap on a new plug (after cutting the old one off, effectively slightly shortening the cord). The old 4-pin jacks had screw terminals for each conductor.
Before the 4-pin plug, telephones were hardwired using a little square box on the wall (with 4 screw terminals inside the cover). Next time I have access to a graphics terminal I will look for a picture and post it. I think South Korea still uses the 4 pin.
Colombia and Venezuela used to use a 2-round pin plug/socket very similar in dimensions to a Europlug!!!!
Imagine the confusions this caused for visiting European tourists plugging their shaver into the telephone box. Now most phones sold in Colombia/Venezuela come equipped with RJ-11 plugs and the corresponding jacks are standard in new construction. You can still get the old two-pin system...but it's mostly old-work/replacement.
Re: A common telephone connector#135142 12/21/0209:09 PM12/21/0209:09 PM
The American modular plug has become the de facto world standard, but there are complications, as not everywhere which has adopted it wires the jacks the same way. Ireland uses it now, but the line is always wired on the outside pair (what would be the yellow/black pair in the U.S.) and they use one side of the inner pair as a bell feed in the same manner as U.K. wiring.
Although in general I like American NEMA power connectors, I have to side with Sven on this one and say that I don't like the modular telephone jacks at all. The plastic clips break off too easily, and they're not at all easy to use for anyone with limited dexterity in their fingers. The old 4-prong jacks were far superior in my opinion (BJ will know from another forum that I've just recently been searching for a source of these!)
Another point: The modular jacks and plugs are used at the telephone end of the cord as well. That means that if one end of a cord is connected to a phone line there will be exposed voltages (up to 50V DC and 90V+ AC ringing) on the other end, easily touched.
Although the U.K. has its own design of modular jacks (just as bad if not worse than the U.S. types, I have to add), we are seeing the U.S. modular plug at the phone end used here as well now. In some cases, the latch clip is shortened so that the "live" end can only be removed by using some sort of tool (e.g. a very fine-bladed screwdriver).
Trumpy, Strictly speaking the RJ designations refer not to the plugs/jacks themselves, but rather to the way in which they are wired. The RJ means Registered Jack, and the numbers were standardized by AT&T/Bell under their USOC system (Uniform Service Order Code).
RJ-11 just happens to have stuck as the name because this is the wiring arrangement for a standard single-line jack as used in most domestic installations.
The same plugs/jacks can be used for other arrangements. For example, a two-line system (line #1 on red/green, #2 on black/yellow) is properly called RJ-14.
Re: A common telephone connector#135146 12/26/0201:03 AM12/26/0201:03 AM
There was a 3rd wire bell configuration in older installations but it hasn't really been used for a long time. Some configurations also exsist that use the outer terminals on the RJ 11 to trip out other sockets during a call. I'm not sure how it works exactly.
Touch tone/modern ringers have been the norm in new installations since the early 80s. Older installations would have used "headphone style" jacks or have been hardwired.
Using UK specified phones in Ireland:
Generally BT branded phones in particular use RJ11 connectors on the back of the phone that carry the signal on the outer two pairs. In order to use them you generally need to use a BT to Irish adaptor with a capacitor in it. (they're small and cheap and readily available)
Other UK equipment can be used simply by plugging in a normal Irish phone cord in place of the BT style one. 3rd wire ringing requires the adaptor with capacitor however.
Caller Display is also different. Eircom uses a long first ring to activate caller display equipment where as BT inverts the line polarity.
Re: A common telephone connector#135147 12/26/0206:44 AM12/26/0206:44 AM
I stand corrected on the Irish jack wiring. I was working from memory of a document I saw a good few years ago -- Obviously my memory wasn't good enough!
The link you provided has a lot of interesting details. From the diagram on page 5, it appears the bell feed is wired onto pins 2 and 5 of the jack (i.e. what would be both sides of the black/yellow pair in America). If this is standard, then the UK/RoI adapters shouldn't need their own capacitor, just wire (UK-Eire) 2-4, 3-5, 5-3 and it should work.
Interesting that the standard wiring also parallels the line to pins 1 and 6. You mentioned equipment seizing the line (e.g. an auto-dialer). Looking at the diagram, my guess would be that such equipment takes the incoming line on 3/4 and returns it on 1/6. All that would then need to be done is to cut the two links at the master jack and the unit can cut-off the line to all other jacks.
By the way, it took me a while to get used to that single-frequency 425Hz Irish dial tone when I was over there. It sounds just like a British number-unobtainable tone!
[This message has been edited by pauluk (edited 12-26-2002).]