# DSL and a 2 line phone



## ang_hammarad (Aug 16, 2005)

I have what I think is a pretty unique trouble involving an SBC DSL customer that has 2 lines to his home. His first line is a POTS line that is used as his main line. This line is on copper from the Central Office all the way to the customers home(Approx 15kft). His second line is the DSL line. The DSL for this line is RT based(Copper portion of the line is approx 6kft). He uses this line for a 2nd voice line, fax and DSL. The trouble is that when I try to connect his 2 line phone to the two lines, I get a hum/buzz on line 1 when line 2(DSL) is plugged in. Also, the other phones in the house that are on line 1(4 phones total) get a hum/buzz too.

The inside wire is "daisy chained" throughout the house(one continuous wire cut in at each jack location).
I used the existing inside wire(3pr cat 3) and did the following: 
1) Installed a nid splitter in the network interface box.
2) Ran Line 1(POTS) into the house on blue/white.
3) Ran Line 2(DSL) from the filtered side of the nid splitter to the jack for fax/voice on orange/white.
4) Ran Line 2(DSL) from the unfiltered side of the nid splitter to a seperate jack for DSL.

So, the jack I installed in the office is a 3 line jack. The top jack is Line 1(POTS) blue/white, voice only. This jack is plugged into L1 on the bottom of the phone.

The middle jack is on orange/white(filtered DSL) for line 2 of the phone and his fax. This jack is plugged into L2 on the bottom of the phone.

The bottom jack is on Green/White(unfiltered DSL) for the DSL modem only. 

The hum is on the line when the 2 line phone is the only phone plugged in. The fax and DSL modem, as well as the other phones in the house have no effect on the hum. The 2 line phone is an AT&T model 922. It was purchased at Staples 3 days ago. If I seperate the lines and put line 2(DSL) to a different phone, there is no hum. Also, I sent another POTS line (copper loop) to his house instead of his DSL line and used that line as his line 2 and there was no hum.

Thanks for taking the time to read this.


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## JamesO (Mar 30, 2005)

By hum I assume you mean 60 Hz line frequency hum and not DSL line noise or caller ID data noise (caller ID noise is usually only heard using a telephone test set in line monitoring mode)?

First thing I would suggest is swap the wire polarity on one line feeding the 2 line phone jack and see what happens. This is a quick and easy test, regardless of whether the polarity is correct on both lines or not. 

Given the wiring is daisy chain, it is unclear at this point if you have been inside each phone jack and if you are trying to use 2 line phones at other positions in the house. My guess would be there is a wiring problem in another jack in the house on the pair you are using for line 2. Most 60 Hz hum that is not on the telco side is usually a wiring problem at a jack. 

I would first disconnect all other phone equipment in the house and see if this changes anything with the hum on the 2 line phone. This should include answering machines, alarm boxes, satellite receivers, TiVo boxes and the likes. Last problem I ran into was a DirecTV TiVo box was plugged into a incorrectly wired wall jack that caused hum on a line with DSL and the DSL was very intermittent. Pulled the wall plate and reworked the wires correctly and life was good. I have also run into pinched wires on wall phone metal plates causing hum. The painters removed the wall plate during a paint job and when they reinstalled the plate, they pinched a wire that took months of phone slamming before the insulation finally was compromised enough to start a 60 Hz line hum and the DSL to not work most of the time. I could not even see the cut in the insulation, however, loosen the mounting screw 1/2 turn and hum was gone. Repositioned wiring and problem solved.

If the pair for Voice Line 2 is present at all positions in the house where 2 line phones are not needed and you may want to disconnect this pair and make sure both wire and connections are well insulated. 

If this phone is a "feature" phone with speaker phone and/or handset volume control, I would suspect this as a possible contributor as well. Many of the speaker phones use external power and this can sometimes be the source of ground loops for 60 Hz hum along with bad station wiring. You may want to also try a different brand/type of 2 line phone just to make sure the phone is not a contributor.

Good luck and let us know what solves the problem.

JamesO


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## johnwill (Sep 26, 2002)

Purchase a DSL splitter and install it at the telco service entrance. Run a direct line from the DSL port on the splitter directly to the DSL modem. Connect all of the other phone instruments to the telephone output of the DSL splitter.

This is as good as it gets for DSL installations, and will usually solve in-house wiring issues.


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## ang_hammarad (Aug 16, 2005)

I have a splitter/filter in the NID now and have his IW connected that way. I moved out to the NID with his phone and with both lines plugged in there, the hum/buzz is still there. I guess my question is if anyone knows if 2 line phones used with DSL need different filters/internal circuitry. 

And like I said in the 1st post, if I use 2 POTS lines, there is no hum. Even if I use the DSL facilities to the customers house.

I have changed the facilities that the DSL is on as well as the facilities his 1st line is on. I have changed the Office Equiptment on both lines as well.
There is hum at the Cross Box with his 2 lines, but no hum with 2 POTS lines. There is hum at the Cross Box with his or any POTS line and any other DSL line. 

The only time that the customers phone does not hum with a DSL line in L2 of the phone, is at the RT. I use his DSL line as L2 and use a random POTS line as L1. This test is done with only approx. 200 ft of wire in the RT.

I tested with a comdial 2 line phone at the NID and it hums, it does not hum at the Cross Box, but the customers does. A few of the tests are proving the phone may be bad, but a few of the tests are pointing towards a network trouble. 

Individually, each line is within SBC line standard specifications. The trouble occurs only when putting the line into a 2 line phone.

Thanks for any input.


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## johnwill (Sep 26, 2002)

I have a client with Verizon DSL, and they have a multi-line phone with four phone lines, including the DSL line after the filter. They've never experienced any issues with the configuration.


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## JamesO (Mar 30, 2005)

I am starting to suspect a Telco drop problem somewhere. Maybe some unusual pair to pair reaction? 

Do you have a telco test set that can monitor the line unloaded?

JamesO


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## ang_hammarad (Aug 16, 2005)

Each line by itself from the customer prem to the co/rt test within SBC standards. The drops and IW test fine. It is only when I try to put both lines into a 2 line phone that it starts to hum, even at the cross box, with all other wire towards the customer removed.


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## johnwill (Sep 26, 2002)

Get a new phone.


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