We
* have discussed this topic previously and with a careful search earlier posts should be found.
I have a vague recollection of connecting a spare, early 1980s vintage, NTE5A to my Ohmmeter 18C. At 95V the over-voltage device was not triggered. At 500V it operated and displayed a delicate violet glow. Ah, here is a
post that I made on the subject.
If the NTE5A has IDCs, rather than screw terminals, for the network connection (the Openreach side) then there is a strong possibility that there is no over-voltage device present.
For adequate protection, there needs to be a good, low impedance, connection to earth and when the device strikes it should clamp both wires of the pair together and directly to earth.
Ideally you would like to have the same protection for each of your four circuits (at the point where they enter Torr Gorm) as that which is present for every circuit at the exchange end. How often is an exchange zapped by a lightening discharge? Probably never. (Perhaps
Liquorice or
4C could let us know their experiences of such events?)
I'm sure if you could find the right person, to which your request should be directed, Openreach would be prepared to arrange the installation. Obviously money would have to be exchanged.
* The forum community.