[Asterisk-Dev] Exception on 22, channel 5

[Ed Greenberg]

Using Asterisk 1.0.9, with a TE405 card, and a 24 channel voice T1, I get 
this:

Exception on 22, channel 5

The call was from a Cisco 7960 (SIP) to a Zap channel (5).

What does 22 mean? What causes this?

Here it is in context:
Oct  5 11:27:54 DEBUG[3101]: Dialing '18779969646'
Oct  5 11:27:54 DEBUG[3101]: Deferring dialing...
Oct  5 11:27:54 VERBOSE[3101]:     -- Called r1/18779969646
Oct  5 11:27:55 DEBUG[3101]: Exception on 22, channel 5
Oct  5 11:27:55 DEBUG[3101]: Got event Hook Transition Complete(12) on 
channel 5 (inde
x 0)
Oct  5 11:27:58 DEBUG[3101]: Exception on 22, channel 5
Oct  5 11:27:58 DEBUG[3101]: Got event Dial Complete(9) on channel 5 (index 
0)
Oct  5 11:27:58 DEBUG[3101]: Enabled echo cancellation on channel 5
Oct  5 11:27:58 DEBUG[3101]: Ooh, format changed from unknown to ulaw

and then, a few seconds later:
Oct  5 11:30:55 DEBUG[3101]: Hangup: channel: 5 index = 0, normal = 22, 
callwait = -1,
 thirdcall = -1
Oct  5 11:30:55 DEBUG[3101]: disabled echo cancellation on channel 5
Oct  5 11:30:55 DEBUG[3101]: Set option TDD MODE, value: OFF(0) on Zap/5-1
Oct  5 11:30:55 DEBUG[3101]: Updated conferencing on 5, with 0 conference 
users
Oct  5 11:30:55 VERBOSE[3101]:     -- Hungup 'Zap/5-1'
Oct  5 11:30:55 DEBUG[3101]: Exiting with DIALSTATUS=CANCEL.
Oct  5 11:30:55 VERBOSE[3101]:   == Spawn extension (tollfree, 18779969646, 
2) exited
non-zero on 'SIP/3630-15c5'

What part of Asterisk said DIALSTATUS=CANCEL. What does is really mean. 
Does it mean that the sip phone sent a CANCEL message to the switch?

Thanks,
</edg>