*CLI> zap show channel 1
Channel: 1
File Descriptor: 17
Span: 1
Extension:
Dialing: no
Context: demo
Caller ID string:
Destroy: 0
InAlarm: 1
Signalling Type: PRI Signalling
Owner: <None>
Real: <None>
Callwait: <None>
Threeway: <None>
Confno: -1
Propagated Conference: -1
Real in conference: 0
DSP: no
Relax DTMF: no
Dialing/CallwaitCAS: 0/0
Default law: alaw
Fax Handled: no
Pulse phone: no
Echo Cancellation: 128 taps, currently OFF
PRI Flags:
PRI Logical Span: Implicit
Actual Hookstate: Onhook
*CLI> zap show channel 2
Channel: 2
File Descriptor: 18
Span: 1
Extension:
Dialing: no
Context: demo
Caller ID string:
Destroy: 0
InAlarm: 1
Signalling Type: PRI Signalling
Owner: <None>
Real: <None>
Callwait: <None>
Threeway: <None>
Confno: -1
Propagated Conference: -1
Real in conference: 0
DSP: no
Relax DTMF: no
Dialing/CallwaitCAS: 0/0
Default law: alaw
Fax Handled: no
Pulse phone: no
Echo Cancellation: 128 taps, currently OFF
PRI Flags:
PRI Logical Span: Implicit
Actual Hookstate: Onhook


And the error I get:
-- Executing Goto("SIP/bruno-116f", "isdn|1|1") in new stack
    -- Goto (isdn,1,1)
    -- Executing Dial("SIP/bruno-116f", "ZAP/1/074001XXXX|20") in new stack
Jun 22 13:45:15 NOTICE[1655]: app_dial.c:759 dial_exec: Unable to create channel of type 'ZAP'
  == Everyone is busy/congested at this time

(I replaced the actual digits in the number with XXXX)