A DB9 serial cable is a computer cable used for data transfer and information between computers and other devices such as modems. The cables achieve this via serial communication protocols and mostly use the RS232 standard.

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Pinout Table

DTE DB9 Pin	DTE Name	DCE Name	DCE DB9 Pin
1	DCD	DCD	1
2	RDX	TXD	2
3	TXD	RXD	3
4	DTR	DSR	4
5	GND	GND	5
6	DSR	DTR	6
7	RTS	CTS	7
8	CTS	RTS	8
9	RI	RI	9

Notes:

• In most cases, DTE is Male and DCE is Female.
• Cable wire colours may vary.
• DCE = Data Communications Equipment (Remote Device)
• DTE = Data Terminal Equipment (Computer)
• DCD = Data Carrier Detect
• RXD = Receive Asynchronous Data
• TXD = Tranmit Asynchronous Data
• DTR = Data Terminal Ready
• GND = Ground
• DSR = Data Set Ready
• RTS = Request to Send Control/Handshake Signal
• CTS = Clear to Send Control/Handshake Signal
•    RI = Ring Indicator