[asterisk-users] TDM 400P in the UK - doesn't see ringing calls hanging up before answer

[Ed W]

Using a TDM400P in the UK nearly works fine, but I have a last remaining 
problem in that if the incoming is ringing and then the caller hangs up, 
asterisk takes another couple of rings before it spots the hangup.

This is annoying in that I sometimes get phantom calls late at night 
(possibly due to call waiting or the exchange doing a half ring to see 
if we are live).  Also I get phantom calls on either the voicemail or 
when I answer there is just dial-tone because the caller hungup before 
the call was answered

I have fiddled with a number of settings relating to polarity reversal 
because I believe that might be relevant to BT's implementation, but 
it's not made any difference from the default config. 

Any suggestions on how to fix this from UK users?  I have tried most of 
the suggestions in the voip wiki to no effect (haven't tried calling BT 
and asking them to change any settings yet)

Thanks for any thoughts

Ed W