asterisk users - Apr 2008 - Asterisk (or maybe Zaptel) goes to "sleep" after inactivity?

Hi all,

Noticed a curious issue in my testing setup for a faxing system I'm putting
together, but it looks like if I let the lines all sit idle for a few days (no
one uses this yet, so the whole thing really does sit idle until I do testing on
it or something else), something I believe on my Asterisk end goes to a kind of
"Sleep".  It's hard to describe really, but I'm not sure if
it's Asterisk itself or maybe the Zaptel side of things.

The whole system is connected by a T1 Tie line to my old Rolm system (a Plain
T1...RBS, E&M Wink, etc..), and on the Rolm side, when this
"sleep" issue crops up, my monitoring there either shows things like
"RING-IN" or "ERROR", but no connection is actually made
between the Rolm and Zaptel, so it's like the Rolm is getting a signal down
the line, but not a signal it likes.  I see the Wink indicators, so I doubt
it's the signalling or anything.  On the Asterisk side, it just says
"Everyone is busy/congested at this time (1:0/0/1)" almost immediately
after Dialing out, and then plays the no-service message.

But once you make a couple of call attempts on the line after a few days of
inactivity, either fax calls via HylaFax or via an IAX softphone I setup for
testing, it all just starts working again, which really baffles me.  Lately, I
also found shutting down Asterisk and restarting zaptel seems to work too. 
It's kinda like getting out of bed after taking a long nap....almost like
the system is groggy and so poking it with a stick (repeated call attempts) or
hit it with a bucket of water (restarting Asterisk/Zaptel) wake it up
(unfortunately, my systems don't drink coffee).

Thoughts perchance?  Asterisk version is 1.4.18.1, and Zaptel is 1.4.9.2.


Thanks!,

--Josh