How to restrict inbound call channels for sip trunk in s-series pbx


In particular case, customer has to restrict inbound call channels to wanted No. but do not restrict outbound call channels for sip trunk, in Yeastar s-series pbx web interface it is possible to limit channels for sip trunk but would matter inbound and outbound call together, in this article we share workaround to restrict only inbound call channels.

Applicable Devices

Model: S-Series PBX

Firmware: Not Required


1. Access ssh of pbx, search and copy similar context in attached pic from /etc/asterisk/extensions.conf and paste to /ysdisk/support/customcfg/extensions_custom.conf, replace ‘sps222’ with sip trunk name accordingly.

2. Comment on one line with colon at header and add a new string to next line in extensions_custom.conf, remember to replace 'sps22' accordingly with sip trunk name and maxchannel to wanted value, in this demo, it is limited to 1 channel, therefore have to replace maxchannel with digit 1.

exten = _.,8,Gotoif($[${GROUP_COUNT(trunk-sps222-endpoint)} > maxchannel]?h,1)


3. Continue to run two commands to make it take effect, do not care warning when executing commands.

support@IPPBX:~$ astconfig

support@IPPBX:~$ asterisk -rx 'dialplan reload'

4. Test calls, new call would drop if everything set up properly.

 PS: If you would like to play a busy message for new incoming call, you can make slight change in extensions_custom.conf like below, busy message can be uploaded to pbx – custom prompts, do not attach audio type in script.

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