Paradise Datacom P300-VSAT Installation & Operating Handbook page 54

If No ESC is chosen then the dialogue ends here, otherwise it proceeds with the Backward alarm option
as follows:
Change, Tx/Rx, Service, Closed Net, Plus ESC, BA Menu
NORMAL
NO BACK' ALM
See "Overhead Rates" in section 8.7.1 on page 137 for details of the overhead percentage requirements
for differing mixes of main data and async ESC data rates.
P300H
Backward Alarm facility:[?]
1=Normal (Back' Alm) 2=No Backward Alarm
A Backward alarm facility is provided causing a deferred alarm to be raised on
this local equipment if the distant end Rx fails for any reason (eg local Tx failure,
or distant Rx failure). The proportion of the overhead assigned to the ESC drops
slightly (68% to 65%), so the overhead may increase marginally to provide the
same async ESC rate.
No Backward Alarm is sent (Tx) or received (Rx) and so slightly more of the
overhead is available to the async ESC, lowering the total overhead marginally.
P300 Modem Installation and Operating Handbook Page 54