On Sep 5, 2013, at 2:58 PM, ard at p850ug1.demon.co.uk (Tony Duell) wrote: Given what everyone has said, that's probably true, though I thought the jack was wide enough to accomodate a 6P plug (the ones that are actually attached to the keyboards are 4P, though). I have quite a few in my basement, but I can't go down to look just now. Fascinating... that's probably the most useless specification I've seen in a while, considering that most Europeans have no need to know a damned thing about FCC regulations. - Dave

On Sep 6, 2013, at 4:45 PM, ard at p850ug1.demon.co.uk (Tony Duell) wrote: Yes, but presumably they actually call them DIN41612 in their country of origin. I've NEVER seen these called FCC68 connectors here, though that doesn't mean no one does. Agreed. It's probably more accurate than RJ11, in any case. - Dave

On Thu, 5 Sep 2013, David Riley wrote: That's pretty much the gist of it. I had to push very hard to get the RJ11, RJ45, etc stuff corrected on Wikipedia but eventually prevailed. The main argument had been that "well, /everyone/ calls them RJ11, RJ45, etc", however in the end, there was plenty of documentation on the misuse of the RJ (Registered Jack) nomenclature.

On Fri, 6 Sep 2013, Tony Duell wrote: Right. Wikipedia now refers to them by their correct name, but both the articles that cover modular connectors and the registered jack standard give some detail on the misuse of the RJxx for modular connectors. The hard part was untangling the huge mess of individual articles for each type of plug and figuring out how to merge/split/redirect content into the correct parent articles while preserving attribution. Planning out how to fix the mess probably took weeks (maybe a month?) while actually implementing it only a day or two once I had it all mapped out. That was definitely not a task I'd want to handle on a routine basis. What I've found very interesting, is how after getting that mess straightened out on Wikipedia, I've noticed a gradual shift on other sites towards using the correct names for modular connectors. People really do read Wikipedia.

On Thu, 5 Sep 2013, Jan-Benedict Glaw wrote: No, generally one should not use a smaller modular plug in a larger modular jack. Most plugs do not have relief slots next to the outermost contacts and the polycarbonate plug body will permanently deform the outer contacts in the modular jack. This happens a lot with 8P8C (RJ45) jacks that people attempt to plug phones into that use 6P4C, 6P2C, etc (RJ11) plugs. There /are/ a few 6P type modular plugs out there that do have relief openings that will somewhat fit 8P8C jacks, but they are very uncommon. The plug fit is still loose and it isn't something the modular plug standards (from Bell System) ever really intended.

This would be a reason to avoid using (eg) a 4p4c plug in a 6p6c jack. But I don't see it as a reason to avoid using, eg, a 4p4c plug in a 6p4c or 6p2c jack. Is there something else I'm missing? /~\ The ASCII Mouse \ / Ribbon Campaign X Against HTML mouse at rodents-montreal.org / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B

On Fri, 6 Sep 2013, David Riley wrote: It would be fine to plug a 6P2C, 6P4C, or 6P6C plug into a 6PxC jack, but not a narrower 4P4C plug (commonly used for telephone handset cords and certain keyboard cables) into a 6PxC jack. The 6P4C or 6P6C plugs are what are sometimes modified to fit the 6P6C OST (offset tab) "MMJ" jacks.

On Sun, 8 Sep 2013, Tony Duell wrote: Right, there would be no outer two contacts to deform in a 6P4C or 6P2C jack as there would be in a 6P6C (or in the case of a 6PxC plug plugged into an 8P8C jack). On the other hand, the physical fit of the 4P4C plug in a 6P4C jack would be loose because the 4P4C plugs have a narrower width body, and moving the cord/plug could cause the contacts to move and introduce noise. This wouldn't likely be a major issue for a telephone application (although I can see no reason to ever use a 4P4C for a telephone line or mounting cord) but this could be an issue where modular connectors are being used for digital signals such as serial connections. As common as 6P6C plugs are, I really can't see a reason to ever use a 4P4C in a 6PxC jack.

Over here (before about 1980), you had to rent all telephones from the Post Office [1]. Most were hardwired, conencted using a junction box known as a 'Blcok, Terminal' (this name now causes a lot of confustion as it's commonly abbreviated to 'BT' on diagrams, and 'BT' happens to be the name now oof a large telecoms compnay here). It was possible to have plug-in telephones (again, you had to rent everything), connected using 4-contact culindrical plugs ('Plug 420'). There was also a 5 contact version ('Plug 505') used for some applications, imcluding Prestel modems. The wirign was plain crazy. I have found ovaer 16 ways these plugs could be wired, a telephone would be different to a fax machine, would be different to an answerign machine, etc. Since I tinker with old phones too, I made a swithcbox which I dubbed the 'deFUBARiser' to let me connect the sockets up any way I wanted to (there are some pictures of this in my flickr account). One reason the GPO wiring was not obvious was that UK telephones of the time had 1k impredance ringers (bells) and if you had several telephones on a line the ringers were in series. This was done so an telehpne could interrupt the bell circuit to prvent the bells tinkling when dialing (of course it was pulse dialing). Quite why this was regarded as so important I do not know. The current UKtelephone connector has 4 contacts, it's similar in concept to the 'modular' connecotr, but tottally incompatible mechanically. The line wires are on the outside 2 terminals (called 2 and 5, there is actually a 6 contat version used for some PABX systems), terminal 4 is local earth (used for party line ringing and earth recall (connecting one side to the line to earth acts like hanging up and starting again) and terminal 3 is the 'bell shunt'.Ringers are connected between 3 and 5, the couplign capacitor for the bell is not in any telephone, it's between 2 and 3 in the 'master socket'. THe idea is that any off-hook telephone can short 3 and 5 to disable all bells, again to prevent tinkle. Actually, most recent telephones and assocaited davices simply use the 2 line wires. Often the drvive has a 6p2c socket for the line cord, this has a UK plug (Plug 431A) to go into the wall and a 6p2c on thbe other end. It is 'cross wired' so pins 2 and 5 of the UK plug end up on the contacts of the 6p2c. UK telephne cables from UK plug to 6p4c therefore exist in 2 versions. Straight (which are not commonly used, except by old US Robotics modems) end up with the line on the outside pair of the 6p4c. Crossover put the line on the centre pair and the earth and bell shunt on the outer pair. One thing I found very difficult to find was the pinout of that 4 pin plug -- which wire went where. I ended up buyign a plug (which fortuanately had the colours moulded into the plastic. I think so. Last time I looked, Old Phone Works had them. -tony