[Asterisk-Users] Sipura spa-2000 / 3000: surge protection

[Peter Hoppe]

Thanks very much for the answer! Yes, the UK has got a very good 
electricity supply - so that wasn't really my worry. What I am more 
worried about are lightning strikes during thunderstorms. And in our 
setting the distance between my spa device and the analog phone can be 
quite long with some of the cable exposed to the outside. I am actually 
working for a charity and I am projecting a new phone system for the 
entire compound. This system would use a bank of spa-2000 adapters 
connected to an asterisk server and three spa-3000 adapters connecting 
to one BT line each. I have looked into using a channel bank (Carrier 
access) but that seems not feasible for us.

We had a lightning strike nearby recently and it went into our existing 
phone system and took one or two ports out (Someone even saw a little 
spark near some electrical appliance in one living room). Thankfully 
there was minimal damage because the phone system (sdx) has got very 
good lightning arresters. That's why I would like to put surge arresters 
in place to protect the fxs ports of my spa adapters. Lightning is 
unlikely, but...

Meanwhile I had a look inside one spa-2000 adapter and I estimate that 
the device can cope with no more than 130 Volts on its fxs port. I 
concluded this from the fact that there are four transistors CZT5551 
near the fxs ports, and the data sheet of that transistor states maximum 
ratings of 180 Volts for Collector-Base Voltage, 160 Volts for 
Collector-Emitter Voltage and 6 Volts for Emitter-Base Voltage. The 
CZT5551 is a NPN silicon transistor designed for high voltage amplifier 
applications. I suspect I should use some design utilizing a 3 pole 90 V 
gas arrester in conjunction with a clamping chip (e.g. TISP 7072) and 
4.7 ohm restistor (plus 100 mA or so quickblow fuse) in series. I found 
a design on

http://www.epanorama.net/documents/telecom/telesurge.html

and I could base my design on the circuit in section

'Non-commercial designs/circuit two'

of that web page. I would use something like a 90V 3 pole gas arrestor
(RS electronics, rs-stock-no 308-8277) and a TISP 7072 (RS electronics, 
rs-stock-no 225-9850). I would like to avoid MOVs, as they tend to be 
destroyed during surge conditions.

But still... if anyone has more accurate voltage ratings, I would be 
very grateful. Thanks already for your answer!

Peter Hoppe





> You would? Why not just put then on a small UPS and have done with it?
> 
> The UK has some of the cleanest electricity in the world.
> 
> Unlike the US (what a big shock that was, moving here) where brown-outs 
> and over volts are common I've never needed to add protection devices to 
> the UK supply.
> 
> Mark
> 
> Peter Hoppe wrote:
>> I am located in the UK, and I am using Sipura spa-2000 adapters to 
>> connect analog phones to a voip network. The network connects to the 
>> PSTN as well via the Sipura spa-3000 adapter.
>> 
>> I would like to provide surge protection for the spa-2000 and the 
>> spa-3000 adapters.
>> 
>> 1.    For spa-2000, fxs port: What is the maximum tip-to-ring voltage 
>> before damage to the the adapter occurs?
>> 
>> 2.    For spa-2000, fxs port: What is the maximum voltage between both 
>> legs and ground before damage to the the adapter occurs? (I have looked 
>> inside an spa-2000 adapter and saw that the board has a ground plane 
>> integrated; the four screw holes seem to connect to that ground plane)
>> 
>> 3.    For spa-2000, network port: Would I need any surge suppression? 
>> What would be a good way forward? I suspect all I need would be some 
>> clamping device on the TX/RX pairs that restricts the voltage?
>> 
>> 4.    For spa-3000, fxo port: Again, maximum tip-to-ring voltage before 
>> damage.
>> 
>> 5.    For spa-3000, fxo port: Maximum voltage between both legs and ground.
>> 
>> Thank you very much for your consideration!
>> 
>> 
>> Peter Hoppe
>> 
>> 
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> 
> -- 
> 
> Mark, G7LTT/KC2ENI
> Randolph, NJ
> http://www.g7ltt.com