Black Box SW928C, SW929C, SW927C, SW925AE, SW926C Connecting to Computers-RS-232 Connections, Cts

MODULAR SMART SWITCH

	Table A-1 (continued).	DB25 Serial Pinouts.
Pin	Description	RS-232	RS-422 In/Out
10	Flow control out (+ve)—hardware		HSOUT + Output
	handshake
11	Received data (-ve)		RXD -	Input
12	Received data (+ve)		RXD +	Input
13	Transmit data (-ve)		TXD -	Output
15	Flow control in (-ve)—hardware		HSIN -	Input
	handshake
16	Flow control in (+ve)—hardware		HSIN +	Input
	handshake
25	Transmit data (+ve)		TXD +	Output

A.2 Connecting to Computers—RS-232 Connections

RS-232 serial ports on computers tend to vary considerably. The standard recommends a DB25 connector, but some machines, such as the IBM AT and compatibles, use a DB9 connector. Computer ports intended for connection to a modem are not configured like those intended for connection to a serial printer. Because of all these variables, a “standard” RS-232 cable does not exist.

NOTE

You might need to refer to the documentation supplied with your computer to establish the type of cable required. The following specifications may help you decide on the required cable.

A.2.1 RS-232 CONNECTIONS TO IBM PCS AND COMPATIBLES

The IBM PC and its compatibles provide a parallel port and (usually) an RS- 232 serial port. Both use a DB25 connector. However, the parallel port is normally a socket (female) connector, and the serial port is normally a plug (male) connector. The cable wiring required for connection to a serial port on the Modular Smart Switch is shown in Figure A-1.

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	MODULAR SMART SWITCH
IBM PC end	Modular Smart Switch end
25-Pin socket connector	25-Pin socket connector
2	RXD
	3
3	TXD
	2
5	DTR
6
	20
7	GND
	7
	CTS
	5
	4

Figure A-1. IBM PC/XT Serial Cable Pinning.

If you already have a cable that works directly between your IBM PC and serial printer, it may be suitable for use as the input cable to your Modular Smart Switch.

A.2.2 RS-232 CONNECTIONS TO IBM AT AND COMPATIBLES

The IBM AT and compatibles provide a DB9 connector for the serial port. The cable required to connect to the Modular Smart Switch is wired as shown in Figure A-2.

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