[Asterisk-Users] Context fails so falling back to extension " s" ?

[Colin Anderson]

>Extension 's'? I thought 's' meant Start, not an actual extension. If
>there's something I'm not reading or need to read again, don't
>hesitate to hit me with a clue stick.

Sort of. 's' is used when there is no matching extension in the context.
It's the fallback extension if there's no match.

http://www.voip-info.org/wiki-Asterisk+s+extension

You don't list your extensions.conf, but taking a stab at it, you would put
in something like:

[from-pstn]
exten => s,1,Dial(YourInternalExtension,15) 'Dial whatever your internal
extension is for 15 seconds
exten => s,2,Hangup() 'Hang up the line if nobody answers. You could put in
a goto to fire the call to the [from-internal] context in
extensions_additional.conf so it can have voicemail logic.

I found that the best part of AMP is they have a really really good
extensions.conf you can use as a template to make a customized dialplan.
Starting from the base AMP extensions.conf and extensions_additional.conf, I
have modified my dialplan *way* beyond what AMP can do, but it's AMP's
template that got me started. I shudder to think of the hours I would have
wasted creating all of the dialplan logic over again from scratch without
AMP giving me a leg-up. Now, I don't even use AMP anymore except for FOP and
the call detail logs. YMMV. 

hth