DCA Intertel s’print BT User Manual page 30

An ACK response is returned in the event the entire protocol was interpreted
correctly and the check sum calculated is the same as that received by the
host.
A NACK response is returned in the event of transmission errors that cause
a discrepancy between the calculated and received check sums.
A BUSY response is returned in the event the printer does not have sufficient
memory to store the transmitted data. If this response is returned, use
the STS byte to find the cause that generated the BUSY condition. If there
are no errors (no paper, head overheating or incorrect electrical voltage), the
BUSY message has been generated because the buffer is full and it is necessary
to wait for the buffer to empty; then change the IDJOB field and repeat
the transmission.
DCA Intertel 30 DCA Intertel