-- Executing [54321@dialplan-extensions:1] Dial("SIP/3051-081faee0", "Zap/8531212") in new stack
[Sep 26 10:27:17] WARNING[2669]: app_dial.c:1106 dial_exec_full: Unable to create channel of type 'Zap' (cause 0 - Unknown)
  == Everyone is busy/congested at this time (1:0/0/1)
    -- Executing [54321@dialplan-extensions:2] Hangup("SIP/3051-081faee0", "") in new stack
  == Spawn extension (dialplan-extensions, 54321, 2) exited non-zero on 'SIP/3051-081faee0'
asterisk2*CLI> zap show channels
   Chan Extension  Context         Language   MOH Interpret
 pseudo            incoming                   default
      1            incoming                   default
      2            incoming                   default
      3            incoming                   default
      4            incoming                   default
      5            incoming                   default