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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?


Patrick T. Caezza
Santa Paula, CA 93060
C-7 - Low Voltage System Contractor - Lic# 992448
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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.

Last edited by 1864; 01/19/14 01:46 AM.

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


Patrick T. Caezza
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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.


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

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

Sam

Last edited by Silversam; 01/19/14 04:40 PM.

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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.


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I know it outdated, but the state is still expecting applicants to know it and it still on the State C-& exams.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


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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.



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Originally Posted by Mercenary Roadie
but the state is still expecting applicants to know it and it still on the State C-& exams.


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.


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I know it's outdated, but the state is still expecting applicants to know it and it still on the State C-& exams.

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


CALIFORNIA PROPOSITION 65 WARNING: Some comments made by me are known to the State of California to cause irreversible brain damage and serious mental disorders leading to confinement.
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