Denso QK20-R User Manual page 51

Communications protocol
You can select either non-acknowledge mode or ACK/NAK mode.
Non-acknowledge mode (default)
If the CTS signal is at a high level (Enable transmission), the scanner transmits code data read.
Note: The configuration software (ScannerSetting_2D) provides a choice of CTS timeout settings from 100 ms to 9.9
s in 100-ms increments and two CTS signal control choices Yes and No.
ACK/NAK mode
If the CTS signal is at high level (Enable transmission), the scanner transmits code data read. After that, the scanner
waits for and then processes a response. If the response is an ACK, the scanner normally ends the transmission; if it is
a NAK, the scanner transmits the code data again.
Note: The configuration software (ScannerSetting_2D) provides a choice of CTS timeout and ACK/NAK response
time settings each from 100 ms to 9.9 s in 100-ms increments.
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