Multi-Tech Systems MMV1600 owner manual Appendix B, Signal Information Negative Positive

Appendix B

RS232C Interface Specification

The MultiMux RS232C interface circuits have been designed to meet the electrical specifications given in the EIA (Electronic Industries Association) RS232C and CCITT (Consultative Committee of International Telegraph and Telephone) standards. All signals generated by the mux are approximately 10 volts when measured across a load of 300 ohms or greater. The receiving circuits of the mux 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 mux 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 mux RS232C interface connector. All other pins are unused. The composite side of the mux is configured as a DTE device and the channel sides are DCE devices.

PIN	MULTI-TECH	EIA	CCITT	SIGNAL	CIRCUIT
ASSIGNMENT DESIGNATION		CIRCUIT CIRCUIT		SOURCE*	FUNCTION
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
B	CD	CF	109	DCE	Data Carrier Detector
9	+V	+V	--	DCE	Test Voltage
15	TC	DB	114	DCE	Transmit Clock
17	RC	DD	115	DCE	Receive Clock
20	TR	CD	108/2	DTE	Data Terminal Ready
22	Rl	CE	125	DCE	Ring Indicator
24	XTC	DA	113	DTE	External Transmit
25	OOS	CN	142	DTE	Terminal Busy

*DTE = Data Terminal Equipment

DCE = Data Communications Equipment

ThecomputerorterminalshouldbesuppliedwithacableterminatedwithaCinchDB25P(orequivalent)connectormountedinaCinch DB51226-1(orequivalent)hoodassemblyasspecifiedbytheRS232C/V.24standard.