3Com 3C16987A manual B Pin-Outs, Null Modem Cable, PC-AT Serial Cable

B PIN-OUTS

Null Modem Cable	9-pin to RS-232 25-pin
	Switch 3300 SM		PC/Terminal
	Cable connector: 9-pin female		Cable connector: 25-pin male/female
	Screen	Shell	1	Screen	only required if screen
	TxD	3	3	RxD
	RxD	2	2	TxD	always required
	Ground	5	7	Ground
	RTS	7	4	RTS
	CTS	8	20	DTR
	DSR	6	5	CTS	required for handshake
	DCD	1	6	DSR
	DTR	4	8	DCD

PC-AT Serial Cable	9-pin to 9-pin
	Switch 3300 SM		PC-AT Serial Port
	Cable connector: 9-pin female		Cable connector: 9-pin female
	Screen	Shell	Shell	Screen	only required if screen
	DTR	4	1	DCD
	TxD	3	2	RxD	always required
	RxD	2	3	TxD
	CTS	8	4	DTR	required for handshake
	Ground	5	5	Ground	always required
	DSR	6	6	DSR
	RTS	7	7	RTS	required for handshake
	DCD	1	8	CTS