Returns the number of channels in the specified group. If no group is specified, the group of the current channel is assumed.
; Query outgoing for number of channels:
exten => 123,1,Set(foo=${GROUP_COUNT(outgoing)})


Internal help for this application in Asterisk 1.4:
  -= Info about function 'GROUP_COUNT' =- 


Counts the number of channels in the specified group

Calculates the group count for the specified group, or uses the
channel's current group if not specifed (and non-empty).
diff output to internal help in Asterisk 1.2:
- none -