Most modern ISDN adapters and support will automatically sense
the condition of "56Kbps ISDN". This occurs when an interswitch
link does not have 64Kbps clear channel and SS#7 support. At this
point the signalling information has to be carried in-band in an
8Kbps channel to the
next node instead of through the SS#7 path. In 99% of the cases
there will be a protocol message that indicates the call has
"left ISDN" or is not "ISDN end-to-end" and at this point the
data transmission can automatically be switched to 56Kbps and the
end user does not have to make any adjustments except to
wait longer for the data
