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#159794 - 01/28/05 01:20 AM Telephone static  
bwise121  Offline
Member
Joined: Sep 2003
Posts: 114
Sacramento, CA USA
An electric gate company installed a gate at a residence. The gate had a key/voice pad at the enterence of the residence for communication. When they were finished the owner had static on his phone lines. I saw that the install used non-direct burial phone lines in the ground and they ran it right next to a 120 Volt feed. Although the 120 is in pvc conduit, could it still cause interference? What are the rules/codes for installing telephone lines near electricity?

thanks,
Byron


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#159795 - 01/28/05 01:42 AM Re: Telephone static  
e57  Offline
Member
Joined: May 2003
Posts: 2,876
S.F.,CA USA
2" is minimum,(800.52(A)2) however more is wise, especially parralel.

But sure it is "static", and not "hum"?

Static can be many reasons. Loose / dirty connection, bad equipment, a whole range of things.

Hum could be induced in the way you described. Especially in PVC or cable. Metallic conduit would afford some shielding effect. Or, the use of shielded phone cable. Both would reduce it to some degree.

Isolate the noise by removing elements of the phone and gate wiring, or shutting off the gate to see if it goes away. If there is an intercom to the gate via phone that could be an issue too.

Wish you luck...


Mark Heller
"Well - I oughta....." -Jackie Gleason

#159796 - 01/28/05 11:00 PM Re: Telephone static  
djk  Offline
Member
Joined: Dec 2002
Posts: 1,237
Ireland
Also remember that a long run of cheap unsheilded phone cable is much more liable to pick up interference from whole variety of sources not just AC cables. It should ideally be properly sheilded if the cable's running a considerable distance to the gate.


#159797 - 01/29/05 12:36 AM Re: Telephone static  
hbiss  Offline
Member
Joined: Dec 2003
Posts: 886
Hawthorne, NY USA
It would be impossible to say what the problem is from the information you give.

I doubt the fact that the cable is not of the direct burial type would be an issue at this point- I'm assuming that it only has been there a short time. It will fail eventually to be sure.

We need to know if this is static as you say or hum. Static would not be caused by proximity to the 120 volt cable, hum would be a possibility.

What is the phone setup in the house- stand alone phones or a system? How many lines and do all lines have the static? How was the gate phone connected to the phones or system?

-Hal


#159798 - 01/29/05 12:01 PM Re: Telephone static  
bwise121  Offline
Member
Joined: Sep 2003
Posts: 114
Sacramento, CA USA
Many thanks for everyone's responses. The owner said the problem was static with a hum. I'm not sure if he is right. I suggested for him to assume the line from the house is okay and have the gate company just splice a new wire from the feed from the house to the control pad at the gate just to see if the problem is resolved. Sure enough, that fixed it. The little jumper is only 15 feet long, so somewhere between those points is the problem. Still not sure what it was.

Thanks to all,
Byron



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