sundance-communications.com/forum Forums Wiring - Telecom Carriers - Trunks & Services Telecom Service & Providers Loop current/ high audio level

Could high audio level from the telco make the PBX user cutout on the TX side of a call. Outside call comes in on analog trunk ShoreTel user answers. Coversation is find at low levels but if the outside caller raises voice to medium high level the ShoreTel user cuts out when they speak at the same time. There are no other issues but this seemingly half duplex issue.
If the db level and loop current is to high on the line for the spec's of the Shoretel system wouldnt the high db level step on the TX side (ST user).

So I would like to reduce the db/loop current on the line. Wouldn't reducing the loop current reduce the db level also and or reducing db level reduce loop current.
I haven't tested the lines yet, but I think this is what is happening. What else may cause half duplex issues?

What is the loop current? Yes reducing loop current will reduce volume some. The clipping would be more of a condition of the IP phone system than the analog line. At least in my opinion. Test from DEMARC to prove this and let us know the off/hook and on/hook voltage and the loop current.

I agree that its probably the ST system. But I have to change the line to meet the VOIP system spec's, that is just the nature of the beast there is no settings I can adjust on the ST system.
I will update with test findings.

Thanks

If the loop current is high you can get loop current regulators from Sandman. If there are other places to get them I'm not aware of it. At least the constant ones. I have found those with different taps, but not near as handy. I'd certainly like to find a less expensive source.

Yeah I was looking at that site. I found the loop current regulator, echo stopper and the telephone line attenuator. I'm thinking the line attenuator looks like it will be my best choice. Since it reduces the db and loop current at the same time.
I just hope that is the issue?

^^^^ What Bill, said.


Is the analog signal and loop current really THAT high at the demarc? Did you test there as Bill suggested? ... And If you’re are going to attenuate for louder conversation what’s going to happen to normal conversation volumes or worse yet for quiet talkers? ... Just something to think about there.

Telephony is a a science that follows established electrical rules. There ain't any magic here. There are three ways to evaluate and solve telephone circuit problems.

1. measurements

2. substitution

3. hand-waving

As has been suggested, please measure the loop current. Then please tell us what it is. Then we will help you.

Can you substitute an incoming line using some other, proven, (read: non-voip nonsense) technology? Is there a POTS line within wiring distance of the KSU in the building (even if can be temporarily borrowed from a co-operative neighbor)?

Without knowing base-line factors, and comparing them to industry standards; and without eliminating the various parts of a suspect circuit, the rest is hand-waving.

An engineer should not suspect that turn of events. High loop current is not a linear problem.

“Loop current” would be measuring the DC component of what is found on a phone line. Georg Ohm figured out the directly proportional (linear) relationship of voltage and resistance back in the early 1800’s.

A voice signal transmitted over a copper wire is a sinusoidal waveform (AC) positioned on top of the DC component. So now if you meant the “voice signal” that is measurable in decibels, is a non-linear (logarithmic) scale, that would in fact be true.

I think I’ll stand by my concern, since in this case, it would seem an attenuator of any kind would be masking a symptom rather the correcting the issue.