Release Notes for 2.57E.44 PRI firmware

1. V.110 was added to call type for B channel status.

2. Improvements in "busy" detection from central office.

A. Added looking at cause code on the disconnect indicator from central
   office to determine if busy.

B. Made sure modem would get a hangup command if cause was not "Busy",
   this makes modem go back on hook faster.