GTCO Surface-Lit AccuTab - Users Guide - Manual (Page 34)

Surface-Lit AccuTab 34
Your computer may have a 25-pin RS-232C connector, rather than a 9-pin connector. If so,
use the 9- to 25-pin adapter supplied with the AccuTab. The figure below shows how this
adapter is wired internally.
Flow Control
Flow control is the process of regulating the traffic or flow of data between two RS-232C
devices. Flow control prevents the transmission and subsequent loss of data if the receiver
is not ready to accept it. Examples of devices that use flow control are: a printer to signal
buffer full; a modem to indicate carrier detect; and a time-shared computer that services
multiple users on a time-available basis.
There are two kinds of flow control:
 Software flow control is often implemented over communication links where only a
3-wire cable is used (Transmit Data, Receive Data, Ground) or over telephone lines.
The sending device (such as the AccuTab) will immediately stop sending data when
it receives an ASCII XOFF character (CTRL-S, hex 13). Transmission will resume when
it receives an ASCII XON character (CTRL-Q, hex 11). Character flow control will work
with the straight through cable and the null modem cable.