DOS HOSPITALITY (serv.man7). Frequnetly Asked Questions (May 2005) - Sharp EPOS FAQ (repair manual). Page 10

The following message appears when I
try and sign onto a slave machine.

“Master Comms error 00a1”

This is an internal application error
therefore nothing to do with external PC
comms, The likely problem is that the
master machine is powered off or
disconnected or there is a network fault.