UPS RS-232 케이블 결선도

결론은 크로스 케이블?

Pin Assignment for the Serial Port (RS-232C), 25-pin and 9-pin
 

DB-25	DB-9	Name	EIA	CCITT	DTE-DCE	Description
Pin #	Pin #
1		FG	AA	101	---	Frame Ground/Chassis GND
2	3	TD	BA	103	--->	Transmitted Data, TxD
3	2	RD	BB	104	<---	Received Data, RxD
4	7	RTS	CA	105	--->	Request To Send
5	8	CTS	CB	106	<---	Clear To Send
6	6	DSR	CC	107	<---	Data Set Ready
7	5	SG	AB	102	----	Signal Ground, GND
8	1	DCD	CF	109	<---	Data Carrier Detect
9		--	--	-	-	Positive DC test voltage
10		--	--	-	-	Negative DC test voltage
11		QM	--	-	<---	Equalizer mode
12		SDCD	SCF	122	<---	Secondary Data Carrier Detect
13		SCTS	SCB	121	<---	Secondary Clear To Send
14		STD	SBA	118	--->	Secondary Transmitted Data
15		TC	DB	114	<---	Transmitter (signal) Clock
16		SRD	SBB	119	<---	Secondary Receiver Clock
17		RC	DD	115	--->	Receiver (signal) Clock
18		DCR	--	-	<---	Divided Clock Receiver
19		SRTS	SCA	120	--->	Secondary Request To Send
20	4	DTR	CD	108.2	--->	Data Terminal Ready
21		SQ	CG	110	<---	Signal Quality Detect
22	9	RI	CE	125	<---	Ring Indicator
23		--	CH	111	--->	Data rate selector
24		--	CI	112	<---	Data rate selector
25		TC	DA	113	<---	Transmitted Clock

[링크 : http://www.linuxjunkies.org/html/UPS-HOWTO.html#ss6.3]

apcsmart An APCSmart UPS and its computer communicate through an RS232C serial connection. They use it as a character channel (2400bps, 8 data bits, 1 stop bit, no parity) and pass commands back and forth in a primitive language resembling modem-control codes. The different APC UPSes all use closely related firmware, so the language doesn't vary much (later versions add more commands). This class of UPS is in decline, rapidly being replaced in APC's product line by USB UPSes.   [링크 : http://www.apcupsd.com/manual/manual.html#supported-upses-and-cables]