I have been studying for my C-7 Low Voltage contractors License here in Calif. The school I have been going through provides practice tests and a study guide for this license and they are well known and trustworthy.

One part in the study guide and several test question cover telephone cables, but I have never seen the function associated with the colors of a standard 6 wire cable using GRN, RED, YEL, BLK, WHT, and BLU colors like they are using them.

Here is the color to function that is being used in the state test.

GRN TIP/+
RED Ring/-
YEL GND
BLK Used for lighted handset dial
YEL & BLK Used for an accessory like a lighted dial, via a 6-v step down transformer, or as a second line
WHT & BlU Used for optional function such as security signals, speakerphones, automatic dialers, background music, etc

The YEL & BLK as a second like I know, but I never heard of the rest of the stuff.

How old is this and is any of it still used today?

I still find the dial lamp transformers in basements that haven't been used for years. I thought the dial used the 51 type lamp that was 10V?

I would guess the cabling for that could be as old as a rotary trimline WE set from the 60's? or older.

Don't you think it funny that they still have that on a state contractors license exam?

JK cable is...pretty much...obsolete at this point. It was usurped by 2 pair CAT3. 2 pair...while still available...has been eclipsed by 4 pair CAT3 and 5E.

It dates (as I recall) from the '70s.

I doubt if it's used at all for anything today.

Sam

Late 70s-mid 80s. It was very popular after the domestic key market was starting to slow and a lot of the newer digital systems used 3 pair concept for station wiring. I still have reels of it I use for hobby projects.

I know it outdated, but the state is still expecting applicants to know it and it still on the State C-& exams.

I am real happy that I broke down and took the Contractors Licensing class as everything I had been studying wouldn't of helped me with the exam.

Also, if you go by what on the exam. You should still be using that cable in new installs.

Here are some random thoughts:

JKT (3 conductors, originally) was used for telephone service that required a ground reference for party-line ringing. It was replaced by 4-conductor wiring when the need for a separate pair came about for lamps.

Quad (4 conductors, twisted into one 4-wire group, but not twisted in pairs) was indeed used in the R/G/Y/B fashion, but there was no "ground" because the Princess ® or Trimline ® transformers were floating supplies. It was a violation to ground one side of them.

Also, be advised that the second pair was also used for A-lead control or for a second line. However, use of quad (2 non-twisted pairs) in lengths that totaled 100 feet or more in a single installation (accumulative 100 feet total to all stations) was forbidden because of cross-talk.

No BOC (Bell Operating Company) with which I am familiar used I/W that had 6 conductors with those colors, although mounting cords for certain ancillary equipment (for example the 107B Spokesman ® speaker) and certain tel sets such as the 510 and 515 used that color code.

The information is at least 30 years obsolete, and no one should be expected to learn, retain, or answer a test with that info. You might ask the examiner if he suggests that students learn all about "knob and tube," if you dare to be so sarcastic.

You might also mention that what you are learning about is called the "odd count" color code, and was MD (Manufacture Discontinued) in the 1970's and replaced with the "even count" color code.

When government or non-Bell (or non-operating company) people try to get involved with the engineering of telephony, you may always expect this type of nonsense to surface. To stray from the topic for a moment, as an example, a few years back, I had the misfortune to be involved in a conversation with an engineer from the mightiest of the mighty communications companies, Motorola, and he kept asserting that "on-hook" meant an active telephone circuit, and "off-hook" meant an idle circuit. I finally just gave up and used equipment from a much smaller company, because I couldn't convince the man that he was full of beans.

I suppose that you should just answer the way you think they want to hear you answer, then go on with your life after you are licensed. I feel your pain, in your pursuit of a license issued by people who are members of the cluelesscenti. I wish you patience and good luck.

Doesn't hurt to know. In my post above I was only thinking about the GRN-RD-BLK-YL..I still see the old 3 cond. GRN-RD-YL in some old houses, when I do the rare residence work.

I like questions like that- it separates the serious from the 20 something jackass IT types. A real phone person would know most of that or know where to find it. If you apprenticed in the trade and studied telecom history and/or have experience (like you are SUPPOSED to to take that test) I expect you would have come across it at some time.

-Hal

That would be true if this was for a telephone contractor's license, but it's not. There is more to Low Voltage than just telephone and you can go your whole career without ever touching a phone system and still have tons of Low Voltage work experience.

It's going to be interesting to see what on the test that counts when I finally sit for it. I just found it interesting that the test would have so much outdated question on it.

Nothing surprises me when it comes to government licensing.

I have a good friend who at one point was trying to get the NYC license to be a shop teacher. In order to get the license he had to show proficiency on a particular model of printing press. Now mind you, there were no longer any classes being taught on printing presses, everything was being taught on computers. But you still needed to show proficiency. Not a problem, except that the type of press you needed to qualify on was manufacturer discontinued.

Not only that there was only ONE UNIT LEFT in the whole world. Guess where it was?

In the testing facility.

But wait! as they say, there's more! The unit was broken and you couldn't demonstrate proficiency, because it didn't work. So for years, no shop teachers were certified. They could work, but couldn't be paid full salary, because they weren't certified.

Happy ending. Eventually (after the problem was publicized, and the administration was publicly mocked), the press was repaired, teachers were certified and -eventually - the testing parameters were changed.

But does it surprise me that there's antiquated information on the test? How long have they been giving this test? Is anyone serious involved in updating it and keeping it current? Who would benefit (or not benefit!) by having a modern, updated test.

Those are the questions to ask.

Sam

While all of the responses are correct, no one actually answered your question. When it comes to "standards" all of the old timers only recognize the "BellCore Specs" as gospel. The BellCore Specs don't actually mention a multi cable with those colors as a station cable.

So, what other "standard" can one turn to? Well, I think, for your test purposes, the FCC Part 68 Rules and Regulations would be the place. In Volume 10, page 151 is a diagram of a 6 position jack. If you extrapolate the jack positions to standard cable wiring, you will see that positions 3 and 4 are Red Ring 1, Green Tip 1, Position 2 Black Tip 2, Position 5 Yellow Ring 2, Position 1 Blue Ring 3 or transformer and Position 6 White Tip 3 or transformer.

If you look at some of the "other" or "Foreign" Electronic Key systems of the 70s and early 80s, you will see Green is Tip, Red is Ring, Black is Data A, Yellow is Data B, White is Speaker + and Blue is Speaker -. There are variations to this, but most are close to this.

When asking about this question, just ask "to which standard are the questions keyed?" If they say NEC or NFPA, you know they have no clue. If they say BellCore or FCC, then you have a fighting chance.

Rcaman

Why does the electrical contractors exam also have questions about classified locations, high voltage, low voltage, fiber optics, fire systems, data and communications? Because the holder of the license COULD perform work in any of these areas. Just because you only want to do one kind of work doesn't mean that you don't need to show your proficiency on the whole of what the license permits you to do.

The state of Ct for instance has a number of separate low voltage licenses that are more specific to type of work the holder does, like telecom, fire systems, security, etc. If you feel that the CA license is too broad perhaps you need to lobby to get it changed and good luck with that. But as far as I'm concerned the more knowledge the better.

-Hal

I don't think it's to broad of a license, I just thought that the information they are requesting one to know was very out dated.

There are even fire alarm system question on it and the license states that it doesn't cover Fire alarm systems.

I was mostly curious about the color coding of the cable and the associated functions as I have never seen or read about those being used before.

I'm not an old telephone guy or even a young IT guy. I'm just and Electronic Technician that has branched out into various other sides of the technology trade as the need arises.

I am proficient in the telephone trade, but by no means an expert and that is one reason I am on this forum as it is the best source of telephone information I have found to date.

Arthur, Thanks for that info and it explains why finding it is so hard.

I see a lot of this JKT cable in older buildings. Really thick gauge wire, like 19AWG or something. I was wondering, should the 3rd wire be left alone if connected to ground at the NI, or should it be disconnected if found? To clarify, is there any reason in today's "modern" telco system to leave the 3rd wire bonded to ground or disconnect it?

I see some of the LEC technicians still wire the yellow wire to ground, even if it is quad wire. Personally on quad, I remove the yellow wire from ground as it makes more of a mess, so I wrap it around the outside jacket (like the black wire) so it is out of the way and can be used a 2nd pair in the future.

No reason to connect the yellow to ground. Where would the other end connect to? Just take the yellow and black and wrap them back.

-Hal