UPGRADING REPAIRING PCs

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Chapter 6—Serial Ports and Modems
External
Device
Figure 6.1 AT-style, 9-pin serial port connector specifications.
Pinouts for Serial Ports
Carrier Detect 1
Receive Data
2
Transmit Data
3
Data Terminal Ready
4
Signal Ground
5
Data Set Ready
6
Request To Send
7
Clear To Send
8
Ring Indicator
9
Tables 6.1, 6.2, and 6.3 show the pinouts of the 9-pin (AT-style),
25-pin, and 9-pin-to-25-pin serial connectors.
Table 6.1 9-Pin (AT) Serial Port Connector
Pin Signal Description I/O
1 CD Carrier detect In
2 RD Receive data In
3 TD Transmit data Out
4 DTR Data terminal ready Out
5 SG Signal ground —
6 DSR Data set ready In
7 RTS Request to send Out
8 CTS Clear to send In
9 RI Ring indicator In
5
9
1 6
Serial
Parallel
Adapter