Black Box MD1640A, MD1641A manual Appendix I RS232C Interface Specifications

APPENDIX I: RS232C Interface Specifications

Appendix I - RS232C Interface Specifications

The Series II Modem's RS232C interface circuits have been designed to meet the electrical specifications given in EIA (Electronic Industries Association) RS232C 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 RS232C standard itself.

The following chart lists the EIA RS232C interface pins and circuits present on the Series II Modem's RS232C Interface connector. All other pins are unused.

Pin	Abbrev.	EIA	CCITT	Signal	Function
No.		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

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