When testing tip to ring, tip to ground, and ring to ground, what kind of resistance should I see (what's normal or within bellcorp specs):
a) with an analog phone on the end, electronic bell?
b) with an analog phone on the end, mechanical bell?
c) with no phone on the end?
This test is being done from the block, with the bridge clips lifted to disconnect the KSU.
Thanks!
Justin
First, a few questions to clear up my confusion:
You say "clips lifted to disconnect the KSU."
Are you testing a pair of wires that runs from an extension output of a KSU towards an analog station?
If so, first be aware that there is no Bellcore standard for KSU extensions, of which I am aware.
Addressing your questions, you should see NO resistance across the pair, or from either side to ground, on a pair that has no resistive fault (by definition). So...the answers to your three questions are:
"none, none, and none."
However, there ARE other parameters that are measurable. Let's take just a pair of wires, without a telephone attached:
Cable pairs that are in serviceable condition should have little or no resistance, (either across the pair, or from either side to ground or to any other conductor in the cable) but WILL have some capacitance that can be measured. Depending upon the length, gauge, and type of wire, and using a kick meter, (KS-8544 "points" meter) you should see:
1. an equal amount of capacitance from each side of the pair to ground (balanced pair)
2. slightly less capacitance (than either side to ground) when you test ACROSS the pair.
3. slightly more across the pair when looking at certain electronic ringers
4. considerably more across the pair when looking at a conventional ringer circuit (REN 1.0A for example)
5. incrementally larger kicks as the number of phones in parallel increases.
6. larger kicks as the length of the pair increases.
7. The kick should decay quickly, which indicates no high-resistive fault, such as leakage in a ringer circuit condensor.
I doubt that in a building with a KSU or a PBX that you will see any perceptible line capacitance kick, because the length of the pair is probably going to be less than 500 feet, which is represented on the kick meter as one "point."
Ten points (measuring from either side to ground) equal a mile of cable, in general.
If the kick meter indicates LESS than 15 points of resistance, or 15 volts of cross battery, you can use the pair with impunity. Over 15 points, or volts, and you will get service that fails completely, or at least is noisy or has hum.
An unbalanced pair (one that has a higher kick on one side versus the other) will cause hum and crosstalk. As little as one point of unbalance per mile of cable will cause a perceptible hum.
The kick meter is a tool used to find rough measurements. Using a different piece of test equipment, namely, an "open meter" will allow you to see the actual length, with an accuracy of less than a foot, of a piece of wire. Open meters cost quite a bit, and mostly are used by LEC field technicians to pinpoint faults in OSP.
Nice info Arthur...I wish I knew half of what you have forgotten over the years.
Merrit, I have a feeling that "half of what you have forgotten over the years." isn't much. Arthur usually can answer any question you suspect he has experience with! (That's a compliment and a thank you, Arthur, something that 1-2 poster's don't understand or do, as we have previously discussed)
Thanks for the info, Arthur. The test is essentially on a pair of wire, from one end where it terminates on a block to the other end where it terminates on a jack and does or doesn't have a phone attached. I threw in the info about the KSU because we're testing next to it, but have pulled the bridge clips to prevent connection to the system while testing.
Justin
You're welcome, Justin.
If you see any resistance, it will be probably be due to moisture and/or crud in the jack, a notorious place for trouble.
When I wired Lenox Hill Hospital back in '85, we installed a GTE CO. The switch came with a Test Desk (built by "Badger", as I recall). The unit would split the circuit and let you look into the switch (to check for DT) or look out into the plant, where you could perform a variety of tests.
The campus was fairly large and (because of all those pesky doctors and patients) annoyingly difficult to get around. Our on-site repairman, whenever he got a trouble, would "look at it" with the Badger. He had a cheat sheet of what a 2500 set (metallic ringer) looked like, what a flash com set (electronic ringer) looked like, what an Electronic Key Set looked like, etc.
It saved him a ton of time, as far as going back and forth and having the right material each time.
I would think a handheld kick meter could help out immensely on a big plant.
Sam
All the really big plants where I worked were 701B step-by-step PBX's.
They all had a New York Tel "special assembly" (read: home made in the shops at Hudson Street) test meter, which consisted of a big commercial bakelite multi-meter, flush-mounted in a sheet metal cabinet. The sloping front had a bunch of switchboard lever keys to reverse polarity, switch from loop to ground metering, and to provide ringing, monitoring, and talking. It had a #6 dial on the front that operated a circuit that would access all the test connectors, one for each 100 group of lines.
I wish I had saved one for my museum's 701. (sigh)