I tried that but it didn’t worked as it seems that asterisk is collection the number before it jumps into the context and start the extension matching if you activate overlapdial.
Without overlapdial the phone is directly jumping into the “s” extension (as it would do if you use immeadeate=yes) it seems like the dialplan handling for ISDN is not the same as it is for analogue phone etc.
Normally i would expect that the number would be analysied on a digit by digit manner till the number could be matched or not matched in the dialplan without overlapdial. (As overlapdial should be used for germans “Nachwahl”.) It seems like the number analysation of ISDN simply isn’t working as it should and using overlapdial … is a trick to get it somehow working anyways.
Maybe the problem is that asterisk needs a channel to send dial tone back to the phone as soon as it recives the DSS1-Setup message of the phone. I guess it would be possible to build a general “s” capture extension that collect the number with WaitForDigits and than jumps to the correct extension block. … but i don’t like that idea.
or i simply do something wrong, don’t understand it