# ISDN and HDLC

**URL:** <https://community.asterisk.org/t/isdn-and-hdlc/22812>\
**Category:** Asterisk Support\
**Created:** [September 1, 2008, 10:01am UTC](https://community.asterisk.org/t/isdn-and-hdlc/22812 "2008-09-01T10:01:28Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Sascha\_Broich](https://avatars.discourse-cdn.com/v4/letter/s/3bc359/32.png) [@Sascha\_Broich](https://community.asterisk.org/u/Sascha_Broich)\
**Post date:** [September 1, 2008, 10:01am UTC](https://community.asterisk.org/t/isdn-and-hdlc/22812/1 "2008-09-01T10:01:28Z")

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Hi,

I updated asterisk from 1.4.2 to 1.4.18.1 and got a problem.  
The HDLC mode of ISDN don’t work any more. As I figured out, the cause of this lies in the “handle\_event” function in “channels/misdn/isdn\_lib.c”.  
Up to 1.4.11 the function “setup\_bc(bc)” is only called for EVENT\_SETUP\_ACKNOWLEDGE. From 1.4.12 on it is also called for EVENT\_SETUP.  
The result is a too early call of setup\_bc. Even before the configuration is loaded. So the HDLC mode can’t be enabled for the channel.  
After changing this part of the function back it works again.  
I wonder if this is a bug or if there is an other way to enable the HDLC mode properly.

Regards,  
Sascha