-- Starting simple switch on 'Zap/4-1'
[Apr  3 14:57:52] NOTICE[2572]: chan_zap.c:6376 ss_thread: Got event 18 (Ring Begin)...
[Apr  3 14:57:53] NOTICE[2572]: chan_zap.c:6376 ss_thread: Got event 2 (Ring/Answered)...
  == Starting Zap/4-1 at incoming,s,1 failed so falling back to exten 's'
  == Starting Zap/4-1 at incoming,s,1 still failed so falling back to context 'default'
[Apr  3 14:57:53] WARNING[2572]: pbx.c:2470 __ast_pbx_run: Channel 'Zap/4-1' sent into invalid extension 's' in context 'default', but no invalid handler
    -- Hungup 'Zap/4-1'