There is not a ring counter, however, if you are using standard US ringing, each ring cycle is 6 seconds, there is a standard for this defined as 2 seconds of ringing followed by 4 seconds of silence…  see https://en.wikipedia.org/wiki/Ringtone for some generic information

From: freeswitch-users-bounces@lists.freeswitch.org [mailto:freeswitch-users-bounces@lists.freeswitch.org] On Behalf Of Ned Ludd
Sent: Tuesday, August 30, 2016 1:27 PM
To: freeswitch-users@lists.freeswitch.org
Subject: [Freeswitch-users] Voicemal ring count

Is there a way to make a call go to voicemail if it's not answered after a certain number of rings?  I can use "call_timeout" to send it after a certain length of time, but I want to do it after a certain number of rings.

Extra credit if you can make it a variable, so I can set the number of rings per user.

Thanks.

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Ned Ludd