atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Cabling Telephones Systems Wiring Measuring loop current on POTS LS line

I have a location I need to get the loop current measured on four LS POTS lines. I can't go myself and I want to make sure the process is correct when I dispatch someone to do it.

In the old days I would use my 145B meter. (or was it 143B...gee that was 29 years ago...)

Anyway, I'm having equipment problems and now I need eliminate high loop current as the possible cause.

In the old days we would use our test set clipped on the meter and go off hook and measure the loop current. 23ma was the minimum we were allowed to pass for installation and turn up. Voltage, resistance and current. I assume the resistance/load at that time was equivalent to 1 REN. (one Bell standard ringer I've always assumed.)

The question is: should the loop current be tested trying to use a 1 REN equivalent or should it be tested using the equipment of the actual equipment connected to the line which is(REN of 0.1 B). I'm leaning toward the equipment on the line at this time. What process would you use? A current meter in series with the line loop? What would you consider a high/possible destructive loop current?

I've seen the loop current limiters Sandman used to sell but have never needed one until now...maybe. Thanks!

The current will be the same no matter what method above you decide to measure it with. I've always just used a butt set. I have also used an old 500 set.

Your second question is just any meter that has a milliamp reading in series. 23ma is optimal I don't like to see it more than 30-33. If I can find my book I'll come back and post the low good high.

Not as hard to find as I thought. Low 11-22 good 23-27 fair 28-34 high 35-44 extreme >45

I've got many places around here 50 or better and do use Sandmans limiters with great success.

JustBill,
Thank you for the info and current ranges. I will get the loop current checked and proceed from there depending on the readings.

I heard some time ago that Mike Sandman was selling the business...then I didn't hear much more about it. Thanks again! DT98

For the benefit of readers of this thread, REN is Ringer Equivalence Number. It is the AC resistance of a ringer. (Bell, electronic ringer, relay, whatever) By definition, Loop Current is a DC value, the current flowing in the subscriber loop. DC is referred to as Resistance, while AC is referred to as Impedance.

The Figure of REN is an indication of the total RINGING power on the loop, when the C. O. is sending out a Ring. Ideally there is 5.0 REN at the demark. Usually there is, IN TOWN. Out in the 'country', not necessarily so. I have been places (as Bill and others here have, I'm sure) where there was a telco ring booster on the customer prem, because the REN was 0.5.

Back in the old days, Ma Bell would run tests on phone lines to determine if someone had more phones than they were paying for. I think the testing involved measuring the REN and comparing the measured results to the calculated ones.

which is why you find a lot of old 500 and 2500 set with the ringer disconnected . if it didn't ring they didn't know it was there

The test desk would read the capacitors on the ringers. The more ringers, the more capacitance.

I put a GTE CO into Lenox Hill Hospital in NYC. The plant was large and consisted of multiple buildings of various ages that were not interconnected on all floors. It made repair much easier to "look" at the set with the test desk. It cut back on a lot of wasted trips.

Sam

https://www.hermonlabs.com/Products/innerData/pdf/Analog%20Telephony%20Overview.pdf

If you click and save this document, you will have all the basic electrical requirements available for reference.

Good doc Arthur!

Thanks.


Sam