Strange ISDN behavior - but Voip working fine ???

Hello:

Seeing a working config that I need some clarification..please!!

5 channels configured on an ISDN Pri for VoIP - these 5 channels show admin'ed
down, channel 23 up/up (spoofing)....VoIP working fine though - both inbound
and outbound calls......when I call in to the site, #show isdn active and
#show voice call status - shows the active call !!

How is ISDN working in this case? Any insight is appreciated.

Thx.

CN

snippets of the config:
controller T1 0/1/0
 framing esf
 fdl both
 linecode b8zs
 cablelength long 0db
 pri-group timeslots 1-5,24

Serial0/1/0:0 unassigned YES unset administratively down
down
Serial0/1/0:1 unassigned YES unset administratively down
down
Serial0/1/0:2 unassigned YES unset administratively down
down
Serial0/1/0:3 unassigned YES unset administratively down
down
Serial0/1/0:4 unassigned YES unset administratively down
down
Serial0/1/0:23 unassigned YES NVRAM up
up

sh int s0/1/0:23
Serial0/1/0:23 is up, line protocol is up (spoofing)
  Hardware is DSX1
Received on Tue Jul 21 2009 - 13:24:59 ART