[Asterisk-Users] Vonage, PSTN, 911, and hardware question

[Henry Devito]

See the attached file I think it will help you.
-----Original Message-----
From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Greg Hill
Sent: Saturday, October 09, 2004 9:06 PM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [Asterisk-Users] Vonage, PSTN, 911, and hardware question

On Sat, 9 Oct 2004, Rajeev Sharma wrote:

> And, back to this question:
>
> 2. Phone availibility during a power outage is a big concern. I'm planning
on keeping my regular
> PSTN line around for emergencies and 911 dialing (so that 911 calls
actually go to the 911 center,
> along with my address). Is there an easy way for all the phone jacks in my
house to automatically be
> switched to the PSTN line if my broadband goes out? I'm also planning on
hacking together a powered
> switch so that when the computer's power supply goes down, the line gets
switched fully to the PSTN
> line, but I'm hoping somebody can give me a better solution.
>
> Anybody have any suggestions about this?

honestly... that really is the way it's done. Many PBXs have a two-pole
relay for each incoming phone line. When the PBX is powered up and
operating normally, the relay is pulled in. When the PBX loses power or is
in some other non-operational state, the relay is released so that the
line is switched over to the backup phone.

It might seem more elegant to do something with transistors or other
components, but when you consider simplicity, reliability, and ease of
implementation, it's hard to beat an old-fashioned relay.

I haven't heard any confirmations, but I imagine that the same technique
is used in devices like the sipura 3000 which switch their output to the
POTS input line automatically during a power failure.

Greg


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