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
_______________________________________________
--Bandwidth and Colocation sponsored by Easynews.com --
Asterisk-Users mailing list
Asterisk-Users at lists.digium.com
http://lists.digium.com/mailman/listinfo/asterisk-users
To UNSUBSCRIBE or update options visit:
http://lists.digium.com/mailman/listinfo/asterisk-users
--
Mark, G7LTT/KC2ENI
Randolph, NJ
http://www.g7ltt.com
_______________________________________________
--Bandwidth and Colocation sponsored by Easynews.com --
Asterisk-Users mailing list
[email protected]
http://lists.digium.com/mailman/listinfo/asterisk-users
To UNSUBSCRIBE or update options visit:
http://lists.digium.com/mailman/listinfo/asterisk-users
