atcomsystems.ca/forum Forums TDM Business Telephone Systems Panasonic Telephones & Systems Coss-talk vs. dropped calls and privacy failure

Dr.'s office with nine locations, four voice lines and fax line. Panasonic four-line with intercom. Eight KX-TS4100 and one KX-TS4300 (with TAD).

First trouble: crosstalk. This is very no good for patient privacy. Loop current 49-50-mA. Installed loop current attentuators, loop current 25mA. Great, no cross-talk. Except now the users are experienceing erratic system operation: dropped calls, unintended barge-in on busy line via auto line select. (This off-hook line selection feature can not be disabled, only can assign lines one, two, three, or four. I suggested that they select a line prior to lifting handset, for temporary relief of unintended barge-in.)

Because the system communicates on line one, I thought maybe removing the attentuation from line one would correct sytem operation. No such luck. Now they have cross-talk and still dropped calls.

The phone company says that anywhwere from 20- to 120mA is acceptable. I believe it should be more like 23-to 35mA.They tried to "load" the lines (ESS5 CO) with no reduction in loop current at all.

I can get a loop current regulator which can be stepped down by dip switch settings. Maybe I can lower loop curent just enough but not too much with this units.

I have spent many hours and a bunch of dough chasing this. Before I spend more time and money I hope some phone dawg out there has some better ideas.

It sounds more like an inside wiring problem.
What system is this?
Is this by chance 2 or 4 line consumer grade phones that can be bought at Costco or Office Depot?
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MrG

Yes, it is a four-line with intercom. Claims to work with up to 16 stations (there are 16 one-touch buttons, default programmed to extensions 11 through 26). Whether it is mass marketed, I don't know.
{{I have one going with five extensions (one is OPX). Existing customer found it on the internet and I agreed to provide and install. It has been working with no complaints since last Fall.}}
This system operates properly on unaltered loop current (ca. 50mA), but exhibits crosstalk. Neither I nor the telco could see any evidence of shorts. With loop current attenuated to 25mA, crosstalk is eliminated, but system operation suffers, particularly: dropped calls on transfer (also reported by local user on hold from afar), and unintended barge-in. Privacy can be released, but has not been.
Does anyone know, or know where I can find, the standards for local telephone loop? I am in Washington state and our regulatory agency referred me to IEEE. I tried ANSI and ATIS. Any other suggestions?

What is your offhook voltage? 5-8 VDC, OK. More, or less, bad news. Also, the P-sonic systems I have installed like that system have the capability of operating with a lower on-hook voltage, i.e. 30VDC rather than 48VDC. Check on-hook voltage and whether or not the 'mother station' is adjustable/progammable for different on-hook voltages. The systems do strange things with working lines that are not supposed to be working. Found out the hardway that some p-sonic systems were shipped with only line 1 'turned on'. I have used 1 of their older systems for several years with no problems at all.

Off-hook voltage is about 9VDC. There is no mother station, just one extension with TAD (not required for system operation).

I visited the site of a system with these same instruments and no problems. Loop current: 39mA, off-hook voltage: 15VDC. I think that if I can get the loop current to reside somewhere nearer that of the working site I'll achieve proper system operation without cross-talk.

Any other ideas?

Thanks for your help.

This is one reason that we do not even touch a system without a control unit. Too many problems like this. It could be you'll have to install new wiring, but no guarantees.

Sounds like you have more than 600 feet of connected station wiring to the "system", which is not hard to accomplish in an office environment. Most manufacturers of these "bargains" advise against this since their proper operation relies heavily upon resistance of the inside wiring cable pairs and precise voltage drops/presence.

Their quoted support of 16 stations assumes wiring standards that are unrealistic in today's office environment. Manufacturers expect "daisy-chain" wiring on 4-line systems, while industry standards expect true star topology.

Mixtures of CAT5, CAT3 and CAT "whatever" further confuse these products. They rely upon 100% perfection with station wiring. That isn't likely to be happening.

I wish I had better news.

Did this setup used to work and now its having the problems? This may be totally off the wall, but the co lines are connected to each phone with 2 line cords, one for co 1-2 and the other for co 3-4. If someone was unplugging and plugging cords in at a phone and happened to get the cords plugged in incorrectly, you'd have a ton of crosstalk............I've had this happen before.
Just an idea.

ictelco VERY GOOD OBSERVATION!

Thanks for the thoughts.
I will check with Panasonic about the impedance concern vis a vis mixture of circuit characteristics. They wre to call me back with maximum loop current (they say 15mA is low end).
Crosstalk is, without doubt, because of the high loop current. When attenuated to 25mA, the crosstalk complaints disappeared immediately and for good.The system started dropping calls, off-hook line select was barging into a busy line (no supervision). One user complained that, after being on hold for a long time, three times was dropped off. Of course, this could have come from afar. She was entirely unable to complete her call. Not good in an office, especially a Clinic. I am sweating this.
Can anyone interpet the useful relationship between, and the electrical/phone network ramifications of: Working site: 39mA, 1.3VAC evenly across the pairs, 51VDC on-hook, 15.1VDC off-hook. At the site in trouble: 50mA,0.0- .5ACV unevenly across the pairs, 50DCV on-hook, 9-9.7VDC off-hook. What I'm looking for is a clue to the likely settings of attenuated loop current, vis avis off-hook voltage. I will try Ohm's law.
If you are interested in this issue check out this old posting:
https://www.sundance-communications.com/cgi- bin/ultimatebb.cgi?/ubb/get_topic/f/1/t/000465/p/1.html
I am convinced that, with the loop current attentuators, I have a fighting chance at achieving sufficient loop current without induced crosstalk. I'll keep you posted.