Thread: Phone line surge protectors

Have you tried ebay?

Here's one
https://www.ebay.com.au/itm/APE-Lapt...sAAOSwVcFalKaB

Thanks Bob. I was just going to post that I found one there.

eBay, who'd a thunk it?


TT

Originally Posted by Twisted Tenon

Thanks Bob. I was just going to post that I found one there.

Protectors do not do protection. Effective protection always answers this question. Where do hundreds of thousands of joules harmlessly dissipate? Best protectors always make a low impedance (ie less than 3 meter) connection to what does the protection - single point earth ground.

Plug-in protectors must somehow 'block' or 'absorb' a surge. How does that 2 cm protector part 'block' what three kilometers of sky cannot? It doesn't.

How does its hundred joules 'absorb' a surge that is hundreds of thousands of joules? Specification numbers make this obvious.

Phone line protectors that are effective must be located where phone lines enter - the service entrance. Only then can it make a connection to the same earth ground also necessary for AC electric, satellite dish, and TV cable. Hundreds of thousands of joules are harmlessly 'absorbed' by earth ground. An effective protector is only a connecting device to what actually does protection.

Originally Posted by westom

Protectors do not do protection. Effective protection always answers this question. Where do hundreds of thousands of joules harmlessly dissipate? Best protectors always make a low impedance (ie less than 3 meter) connection to what does the protection - single point earth ground.

It depends on what you're trying to protect against. A lightning strike to a pole close to the house? That needs seriously heavy duty protection.

The diminishing ripple effect from a lightning strike some distance away? A small protector can be effective. As a matter of fact, I lost white-goods, an answering machine and an UPS from such strike. My main PC and peripherals survived due solely to a power/phone surge protector. (I was running a 24/7 fidonet BBS at the time. Think of it as a pre-internet file & mailserver.)

I still have and use a similar device to TT.

Originally Posted by westom

Protectors do not do protection. Effective protection always answers this question. Where do hundreds of thousands of joules harmlessly dissipate? Best protectors always make a low impedance (ie less than 3 meter) connection to what does the protection - single point earth ground.

Plug-in protectors must somehow 'block' or 'absorb' a surge. How does that 2 cm protector part 'block' what three kilometers of sky cannot? It doesn't. .

Plug-in protectors won't protect from a direct or close lightening strike but most lightning damage doesn't involve a direct hit.
Short of a thick copper rod into the ground nearby nothing will protect a direct hit which is a rare event.

When lightning strikes anything it generates a momentary intense electric field around the strike point including in the ground, water and buildings etc. The field intensity varies roughly inversely proportionately to the distance from the strike depending on V of the initial strike the E conductivity and permittivity of the materials supporting the E field. The E field maybe millions of V/m in the air, maybe 100kV/m in the ground or objects a few meters from the strike point, maybe 10kV/m some 10's of meters from the strike and maybe, if the ground is wet, 1kV/m up to a 100 m from the strike.

If you stand with your legs 50 cm apart in line with the strike on a patch of ground (it could be say 20m from a strike point) where E field is 1kV/m you will experience a shock of 500V between your legs. Large animals like cows with their legs 1.5m apart will experience 1.5kV which is why more large animals are affected by lightening strikes than smaller ones. People have survived a direct low V lightening strike, but some have not survived even though they have been some 10's m away from a high V strike. This also explains why you should stand on one foot in a lightening storm. The most you can experience is the V drop across your foot which is usually 20 cm long but it will not transfer electrical current up to your torso. It also explains why you should not lean up against a tree, fence or building because then the current will go past your heart and may cause heart failure.

The same goes for electronic gear - the lightening can strike nearby (so no direct hit) but the gear can still experience E fields from the strike which can develop high voltages across components and destroy then. Surge protectors can protect up to a point against low to medium values of the E field which is much more likely to occur than a direct strike.

Sometimes you can get really unlucky!
A few years back I was in our lab at work when a large lightening strike hit the surface of flooded car park about 10 m away from the lab. There was an almighty BANG and a flashover (mini lightening discharge) across one of the big (6m long) analytical machines full of sensitive gear inside the lab. The strike formed a 10 cm deep x about 50 cm diameter crater in the carpark and according to an observer blew/evaporated/destroyed the cm deep water away from the strike for a distance of about 10 m.

The lab had a serious surge protector on the incoming 3 Phase power supply, and a earthing strap that consisted of a 25 x 12 mm copper bar that ran around the lab and connected to 3, 75 mm diameter mains copper water pipes about 4m under - guess where, yep the car park. So even though the lightening did not hit the copper rod or pipes directly the E field was so high in the ground it generated enough current so that a high current ran back up the earth strap into the lab and direct onto the machine. The power supply surge protector kicked in but unfortunately it was too late because by then the damage had happened and anyway it was in the wrong direction.

The machine which had originally cost about $400k had been fastidiously maintained and had a replacement value of about a million dollars, but as was about 20 years old it was valued at ZERO $ so we did not get a cracker out of the insurance company. After the strike we refurbished the machine but it was never the same and eventually we had to scrap it and many of the parts were given away to the Uni of Toronto.

Ancient history.

I worked for the phone company, GTE, here in the US. (Also known as the Anti-ATT)

There were two styles of protectors. Both had a carbon disk between either side of the line and ground while the deluxe version had a fuse between the line from the pole and the interior of the building. These protectors worked very well at protecting the land line telephone. (Ya know, that ugly black thing with the round thing that you would spin to talk to someone.) The deluxe version was more prevalent in the mountain (San Bernardino Mountains) areas than the flatlands. I don't know if these surge protectors are good for electronic devices. The reason that I mention this is that Telstra may be able to supply and install a surge protector for your phone lines.

Originally Posted by rrich

There were two styles of protectors. Both had a carbon disk between either side of the line and ground while the deluxe version had a fuse between the line from the pole and the interior of the building. These protectors worked very well at protecting the land line telephone.

The carbons were standard protection before 1950s. When transistors were developed, Bell Labs had to define transistor protection. Except for a few minor corrections, that existing protection from direct lightning strikes and other surges was proven effective.

A telco CO would suffer about 100 surges with each storm. How often are towns without phones for four days while they replace that $multi-million computer? Never. Because protection that long ago (only using the carbons) was that effective and that well understood.

Carbons have long been replaced by superior semiconductor devices. But in every case, no protector does protection. Protection is defined by single point earth ground.

When damage happens, an investigation begins with THE most critical item in every protection 'system' - earth ground. Because a protector (carbons then and semiconductors today) is only as effective as its earth ground.

Any protection 'system' that does not protect from a direct lightning strike (even to a nearby pole) is undersized - probably has a defective earth ground connection. Any protector that fails on a first strike is undersized. Since all this was well understood even over 100 years ago. Since COs used and use this proven solution so that 100 surges with each storm do not cause damage.

Plenty of effective protectors exist for telephones. First, that protector must be low capacitance. Second, it must have a dedicated connection for - this is most critical - a low impedance (ie less than 3 meter) connection to earth ground.

Wall receptacle safety ground clearly is not earth ground.