Humzapper, INT Reduce PBX Noise

by J.G. Humpres, Hotliner Pro

Several months ago we installed four off premises extensions. The two buildings were about 1500 feet (457 meters) apart with no tie cable between the two locations, so it was necessary to tie the two together through our Central Office. Cable routes now feeding these locations totaled 29,000 feet (8,839 meters).

Within a week after installation the customer reported a loud hum that would come and go, rendering the circuits unusable. On a return visit all cable pairs were re-tested, but no trouble was found. C-message noise and noise-to-ground readings were all within acceptable limits. AC voltage was measured at both locations and found to be balanced, 6 to 7 volts to ground.

We were sure our outside plant facilities were not the cause of the noise, but convincing the customer and/or their equipment vendor that the noise might be coming from their equipment is not always an easy task.

I decided to give our HumZapper a try. It was installed at the PBX location, with the four lines running through the INT portion of the HumZapper. The noise was present during installation and was reduced immediately upon installation. We left the HumZapper in place for about two weeks. Upon contacting the customer after this time we were told the loud hum had been totally eliminated. A permanent INT has been ordered and will be installed as soon as possible.

Once again the HumZapper has proven its worth. It is a MUST for all technicians responsible for troubleshooting any noise related problems.

Humzapper, INT Team up to Zap Hum

by J.G. Humpres, Hotliner Pro

We have a 25 pair lead in a rural area that has had a very loud hum on all pairs. The T-136 circuit noise readings ranged between 25 and 35 dBrnc, with power influence readings of 98 dBrnc. AC voltage measured in the field is 120 volts at the customer’s AC outlet. Across the cable pair, readings were eight volts tip to ground and eight volts ring to ground.
During my investigation I was informed that the entire lead from the CO to the end had been completely rebonded and grounded with no improvement. There were several connections made between our plant and the power company MGN.

Harmonics were measured using a T-132 spectrum analyzer with 540 Hz measuring 95 dBrnc. While driving the length of exposure, no capacitor banks could be seen. I contacted the local power company to verify that there were, in fact, no capacitors that I had missed. They informed me that they had none in their entire serving area.
I was unsure of what my next step would be, so I decided to give my HumZapper a try, using the INT portion. I placed it at the main frame and took T-136 readings at the far end. No change. Next, I placed it at two locations in the field. This resulted in a drop in noise from 35 to 28, and a drop in Power Influence from 98 to 92. Although only one pair was run through the INT, it was encouraging enough to to place an INT.
The INT was installed and cut through on August 20, 1990. It reduced both C-message noise and power influence readings by 20 dB. At last, no more hum!

The placement of the INT has reduced trouble reports of loud hum to zero. What a welcome relief! To be totally honest, I was very impressed and pleased with these results.

Humzapper Used to Identify Proper Equipment

by M.T. Whatley, Hotliner Pro

We have used the SNC HumZapper on numerous occasions to identify proper SNC equipment to be used and the correct location for installation to achieve maximum results.

Our OSP utilizes 109 iron wire for rural customers, and as a result we experience AC voltage problems regularly. We had one iron wire route that was working out of 914 remote unit that had 32.4 volts of AC on each side of the line. The condition was damaging cards in the 914 unit and causing customer service problems. We installed a SNIX where the iron wire entered the cable.
This resulted in:

• Reduction in AC voltage to .6 volts on each side of the line.

• Elimination of customer complaints.

• No more damaged CO equipment.

The “Rest of the Story” is that the Iron Wire has recently been replaced with cable and we salvaged the SNIX for use on the next “opportunity.”

We have also identified problems and established location for our engineering department to install “INTs” to control and/or eliminate high power influence problems.

SNIX, Humzapper “All in a Day’s Work"

by Charles B. Euler, Hotliner Pro

On April 17, 1992 at 7:30 a.m. a central DSS employee called the local manager to inform him of a line working out of a remote “1218” switch that kept producing an alarm in the central office due to 29 volts of AC on each side of the line. The local manager committed to correct the problem that day and had a repair ticket entered for the cable department. That’s where I got involved.

After being dispatched on the “AC” problem at 10:15 a.m., I stopped by the local manager’s office to pick up a SNIX, then drove about 15 miles to the customer.

My inspections of the area revealed that there were 19 spans of one pair, rural distribution wire about 7000 feet from the cable to the customer. I installed the SNIX on the rural distribution wire at the cable. I then called the central office employee to have them read the line for AC voltage. The AC voltage had been reduced from 29 volts to 2.3 volts – the job was completed by 12 noon.

Problems of this type can be solved quickly and efficiently due to my training and use of the HumZapper to identify problems and solutions. In the past these types of problems could have taken a lot of time to correct, but using SNC products it’s just “all in a day’s work."

Swedish Telecom Has TLC Success

by Lars Ankarbring, Hotliner Pro

We had interference from high voltage power lines between the Järlåsa Central Office (CO) and another office on analog lines. We used Telecom Line Conditioners (TLCs) on both ends to mitigate the noise. The TLC is a combination of an Induction Neutralizing Transformer (INT) and a TEN in one package.

Before installation of the TLCs we used a HumZapper to see if the TLCs would work. The installation was a great success.

SNC Manufacturing Co., Inc. 101 West Waukau Avenue
Oshkosh, WI 54902-7299 Phone: 920.231.7370 FAX: 920.231.1090
E-mail: telecom@sncmfg.com http://www.sncmfg.com