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Rings once and hangs up

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jp61616

Technical User
Jun 16, 2005
83
US
We have a mitel system and were going to run an analog phone to another building for a fax. At both ends we have surgegate 1 GIG Cat 6 Lan surge supressors. The phone line is fine until you punch it into one of the surge suppressors. Then when you dial it the phone rings once and hangs up. Is this the wrong surge supressor for a phone line? It does not make much sense, because you can go to the other end and call OUT - but when you try to call in (like a fax) it rings once and hangs up. Anybody ever heard of that before?
 
It's called a Ring Trip and yes it is fairly common.

A LAN surge protector is not designed for voice. The voice pair (pins 4 and 5 on a RJ45) is unused for LAN connections and it would not surprise me if that is what they use as a way of detecting a surge. Send ring voltage, trip protection cct.

Are the wires exposed (aerial) between buildings? If not, I doubt you need protection at all.



**********************************************
What's most important is that you realise ... There is no spoon.
 
Talk battery is 24 volts and fairly low amperage. Ring battery is 90 vac. It opens the LAN suppressors and trips the ring. Find a voice protector and replace the LAN suppressor

I suppose you're entitled to your opinion, I'm just not to suppose very hard.
 
Talk battery passes through because its 24vdc and low amperage. Ring battery is 90vac and opens the LAN suppressor; grounding the circuit and tripping the ring. Replace the LAN suppressor with voice suppressor

I suppose you're entitled to your opinion, I'm just not to suppose very hard.
 
Thanks! I will replace the LAN protectors.
 
A surge protector rated for higher telephone voltages is required where each wire enters or exits the building. Each protector must make a low impedance (ie less than 3 meter) connection to each structures single point earth ground. If using multiple grounds for any one building, then surge damage can be easier.

Telephone protectors are designed for hundreds of volts. If that protector does not have the dedicated wire for earth ground (not receptacle safety ground), then it is not for telephone line service.
 
@Westom

What you say is true for Aerial/entrance cabling from the Telco. The main reason is to protect from lightning strikes.

It does not necessarily apply to tie cables between buildings in conduit

**********************************************
What's most important is that you realise ... There is no spoon.
 
> It does not necessarily apply to tie cables between buildings in conduit

Absolutely applies. Otherwise a lightning strike to any incoming utility wire in one building means that building acts like a lightning rod connected to Mitel equipment in the other building.

A ballpark number is often used. If two structures have more than 20 feet separation (and still share a common earth ground), then each building must be treated as if completely separate.

Makes no different if wire is overhead or underground. Destructive transients enter on underground wires just like on overhead. All incoming wires must enter at the common entrance - also called a service entrance.
 
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