Using CSIM start to test voice gateways

A neat way to test phone lines on a Cisco voice gateway is to use a hidden command, CSIM.
This will simulate a call that will follow your dial plan and translation rules, the called number should ring (if dialed correctly) and any debug command (e.g. debug isdn q931) will give you a proper output.
Syntax is csim start xxx (where xxx= number to dial)

Example use is:
Router# csim strat 9003923455600

Keep in mind that the called party won't hear anything if he answers the phone and the the output would always display failed.

CSIM it's not documented and I will update this post to reflect any new info.

Also check this if using SSH 

CSIM not working

Well today tried to use CSIM start command to troubleshoot a PSTN line. In my previous experiences it worked fine, but now I had an issue. Command would complete but no call would be made (see output):

So a bit of digging around found that CSIM won't work via SSH.

So use telnet or console to test with CSIM.