[Asterisk-Users] POTS fail-over?

[Shane Young]

Quoting Jay Milk <jay at skimmilk.net>:

> Thank you -- looks like overkill for my app.  Found me a 4PDT relay
> operating on 5V for $5.50 -- This will allow me to switch two lines onto
> two extensions, if needed, and I can run it off a 5V lead in the
> server... Server off => Landline rings extension... And extension
> available for 911, just in case.

I've done this as well several times before.  Many PBX's have the very same functionality built 
in.  The annoying thing is when you are on a call in "power fail" mode and the power is restored, 
disconnecting your call in progress.

The Viking power fail unit will wait for you to complete the call before restoring the "normal" 
condition on the line.  

With a little effort, you could do something similar with a relay, perhaps requring you to hit 
a "reset" button to get it to re-latch.