Surge arrester for telephone line

[earckens]

Does anyone have an idea how to build a lightning protection for a telephone line, may be self-destructive in case of a nearby strike. reason is that our telephone lines are airwire, so fairly sensitive for inductive-type surges.
Since I cannot bury these lines ( ) an alternative approach is needed, ie. install surge protection.

 

[earckens]

Would this one help: T21-A230X ? It has a DC spark-over voltage of 230V, **broken link removed** show it in a design for line protection, but I am unsure if this would/could be effective?

 

[sagor1]

That schematic would be fairly effective, though I would lower the trigger voltages a bit myself. Most land line phones run around 48-56V, and may have spikes in normal use. A 150V gas tube and perhaps 240V MOV would be my personal choice. Be sure to use 3W rated resistors as shown in that schematic.
That all said, the schematic as drawn would work as well. Remember the gas discharge tube is only as good as the ground it is connected to. A simple small wire is not enough for a nearby hit. Put the protection device close to where the phone line enters the house, hopefully close to your electrical panel grounding (earth ground connection).
A direct hit, well, not much will prevent damage, but any good protection circuit should minimize that damage.

 

[rjenkinsgb]

Look for BT or Krone "21A" gas discharge tubes on ebay.
They are the standard type used by British Telecom.
**broken link removed**

You can also get a "BT Magazine 5B" aka Krone 2/10 that takes ten of those and slots directly in to the top of a ten pair Krone 237A telecomms junction block

https://rlcomunicaciones.com/docs/te/60892023-01.pdf

When used with 237A blocks, he ground is via the connection box frame, so that must be properly earthed.
**broken link removed**

 

[KeepItSimpleStupid]

A 150V gas tube and perhaps 240V MOV would be my personal choice.

Don't forget the ring voltage amplitude.

Telephone lines have pretty decent surge protection as it is.

I've had surge devices die. The 60 YO house had carbon for surge suppression. Then a NID was added outside.

The general importance is to have a good ground for the surge to divert too. It could take multiple ground rods.

Unfortunately, it's difficult to do it the RIGHT way because telco and power are way far apart. A cold water pipe is the ground electrode.

Ideally, the ground for telco, power and cable should be referenced to one point. For the most part, telco is independent.

 

[ClydeCrashKop]

A house I had in the ‘70s had an aluminum can outside. They told me it was for telephone lightning protection. It had what looked like fuses inside. I Googled telephone lightning protection. I got plenty of hits but not that unit. What was that? Just fuses?