Epson ES-1000C Reference Manual page 161

ACK
Format:
Explanation:
This code is used by both the scanner and computer for handshaking.
This code indicates that a command, a set of parameters, or a data
block was legal and accepted by the receiving device.
The computer should always send an ACK code in response to a data
block sent from the scanner, except after the last data block of a page
of image data. If the computer fails to send an ACK code within 30
seconds, an interface error occurs in the scanner.
Note:
The ACK code shown here is the ASCII code for 06
does not refer to the ACKNLG signal line of the interface.
Normal response (acknowledge)
ASCII: ACK
Decimal: 6
Hexadecimal: 06
B1 B2 B3 B4 B5 A5
. The ACK code
H
Command Reference
3-67