asterisk users - May 2004 - Problem with digits blending on inbound pulsed digits?

I have a situation where I am receiving DID calls using Immediate Start
Pulse signalling on a Loop Start trunk. The line terminates on a Newbridge
Mainstreet 3624 channel bank, which provides battery etc. The channel is
converted and routed to Asterisk. The lines are configured as follows:

/etc/asterisk/zapata.conf

; Channels 1-24 service MainStreet 3624 channel bank
context=infrom-did
group=1
immediate=yes
signalling = fxo_ls
busydetect=no
callprogress=no
echocancel=yes
echotrain=no
echocancelwhenbridged=yes
debounce=50
channel => 1-4

/etc/asterisk/extensions.conf

[infrom-did]
exten => s,1,DigitTimeout,3                     ; Gather keypresses, 2
second pause is 'completed dialing'
exten => s,3,ResponseTimeout,10                 ; 10 seconds without any
digits is a problem...
include => outto-sip
include => outto-norstar-DNs

Now, the first problem I had was with the first few pulses getting clipped
from the inbound digits. Setting 'debounce=50' resolved that. My current
problem is 'blending' of digits. For example, if I receive pulses for 8
0 1
or  8 0 8 they are correctly recognised almost all of the time. If however I
receive 8 8 8 they are almost never correctly translated. Essentially, it
seems to be something to do with timing for the interdigit gap. I have tried
terminating the lines on a Norstar MICS DID card w/Immediate Pulse and all
digits are correctly received all the time.

Can anyone suggest the appropriate timing parameter to twiddle to adjust the
interdigit detection? Switching to Wink or Delay Start to get DTMF is not an
option at the moment, and my service provider will not custom configure
Immediate DTMF.

I'm running last nights CVS libpri/zaptel and asterisk.

Kris Boutilier
Information Systems Coordinator
Sunshine Coast Regional District