Anyone know what "L1 ERR IF_ACTIVE" means?

Does anyone know what "L1 ERR IF_ACTIVE" means in IOS?

Possibly similar messages during a real L1 problem:
ISDN BR0: Physical layer is IF_DOWN
ISDN BR0: L1 persistent Deactivated
ISDN BR0: L1 is IF_ACTIVE

Saying L1 _is_ "IF_ACTIVE" when it is down and not activated seems
odd...

Message appears occasionally on a working router while no calls are
active:
ISDN BR0: TX -> RRp sapi = 0 tei = 68 nr = 21
ISDN BR0: RX <- RRf sapi = 0 tei = 68 nr = 21
ISDN BR0: L1 ERR IF_ACTIVE
ISDN BR0: TX -> RRp sapi = 0 tei = 69 nr = 1
ISDN BR0: RX <- RRf sapi = 0 tei = 69 nr = 1

Message appears regularly right after connect message:
ISDN BR0: Event: Connected to 17074660517 on B2 at 64 Kb/s
ISDN BR0: L1 ERR IF_ACTIVE

I have to assume "IF_ACTIVE" has some special, non-obvious meaning,
and "ERR" does not mean there is a problem. Searching Cisco and the
web did not turn up any explanation. I guess that means it doesn't
matter much, but it was certainly confusing while I was trying to
debug ATT's problem with my line.

Loren