The compaq R6000 UPS uses a DE9-P (UPS side) to DE9-S (host side) cable

Female (host)	Male (UPS)	Function
1		N/C
2		2		Data to Host
3		1		Data to UPS
4		N/C		DTR (connected to 6 on female end)
5		4		GND
6		N/C		DSR (connected to 4 on female end)
7		6		RTS
8		N/C
9		N/C