gate1*CLI> show channels
        Channel  (Context    Extension    Pri )   State Appl.         Data
        Zap/1-1  (from_bell  s            1   )      Up Bridged Call  Zap/101-1
      Zap/101-1  (from_dialogic 12015537210  1   )      Up Dial          Zap/g1/12015537210
       Zap/99-1  (from_dialogic s            1   )      Up Bridged Call  Zap/13-1
       Zap/13-1  (from_bell  7458         1   )      Up Dial          Zap/g5/7458
4 active channel(s)
    -- Accepting call from '5145556663' to '1909' on channel 0/23, span 1
    -- Executing Dial("Zap/23-1", "Zap/g5/1909") in new stack
    -- Called g5/1909
    -- Channel 0/1, span 5 got hangup
    -- Zap/97-1 is busy
    -- Hungup 'Zap/97-1'
  == Everyone is busy/congested at this time
    -- Channel 0/23, span 1 got hangup
    -- Hungup 'Zap/23-1'
gate1*CLI>


why Zap/97-1 is busy exactly?