Open Source - Running dahdi_cfg: DAHDI_ATTACH_ECHOCAN failed on channel 1: Invalid argument

This is caused by a misconfiguration of the echo cancellation setting in DAHDI. Usually is triggered by an DAHDI update and OSLEC module being not installed. 

Please use the following steps to resolve this issue:

1. Open /etc/dahdi/system.conf with a text editor

2. change echocanceller settings to mg2

3. Save and exit

4. restart DAHDI process