Multitech MT1432BA manual Appendix J RS-232C Interface Specifications, Pin Designation Eia, 156

MultiModemBA User Guide

Appendix J - RS-232C Interface Specifications

The modem's RS-232C interface circuits have been designed to meet the electrical specifications given in EIA (Electronic Industries Association) RS-232C standards. All signals generated by the modem are approximately 10 volts when measured across a load of 3000 ohms or greater. The receiving circuits of the modem will accept signals in the 3 to 25 volt range. The voltage thresholds are:

Negative = voltage more negative than 3 volts with respect to signal ground

Positive = voltage more positive than +3 volts with respect to signal ground

SIGNAL INFORMATION:	NEGATIVE	POSITIVE
Binary State	One	Zero
Signal Condition	Mark	Space
Control and Timing Function	Off	On

The input impedances of all modem circuits which accept signals from the data processing terminal or CPU equipment have DC resistances of 4.7K. For more specific details, consult the EIA RS-232C standard itself.

The following chart lists the EIA RS-232C interface pins and circuits present on the modem's RS232C Interface connector. All other pins are unused.

Pin	Designation	eia	CCITT	signal	Function
Assignment		circuit	circuit		source
1	PG	--	101	--	Protective Ground
2	SD	BA	103	DTE	Transmitted Data
3	RD	BB	104	DCE	Received Data
4	RTS	CA	105	DTE	Request to Send
5	CTS	CB	106	DCE	Clear to Send
6	DSR	CC	107	DCE	Data Set Ready
7	SG	AB	102	--	Signal Ground
8	CD	CF	109	DCE	Carrier Detect
9**	+v	+v	--	DCE	Test Voltage
12	HS	--	--	DCE	High Speed
15***	TC	DB	114	DCE	Transmit Clock
17***	RC	DD	115	DCE	Receive Clock
20	TR****	CD	108/2	DTE	Terminal Ready
22	RI	CE	125	DCE	Ring Indicator
24	XTC	DA	113	DTE	External Transmit Clock
25	OOS	CN	142	DTE	Terminal Busy

**Pin 9 need not be present in your RS-232C cable

***Pins 15 and 17 are necessary only for synchronous operation

****Also known as DTR (Data Terminal Ready)

The computer or terminal should be supplied with a cable terminated with a Cinch DB-25P (or equivalent) connector mounted in a Cinch DB-51226-1 (or equivalent) hood assembly as specified by the EIA RS-232C standard.

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