US Robotics 56K MESSAGE MODEM - QUICK FOR WINDOWS Podręcznik Użytkownika Pobierz pdf (Strona 72)

68 56K Message Modem

The Serial Interface

The serial interface is a standard developed by the Electronic Industries

Association (EIA). It defines the signals and voltages used when data

is exchanged between a computer and a modem or serial printer.

The entire standard covers many more functions than are used in most

data communications applications. Data is transmitted between the

devices over a shielded serial cable with a 25-pin male (DB-25P)

connector to the modem and a 25-pin, 9-pin, 8-pin, or custom-built

connector to the computer.

Pin assignments are factory-set in the 56K Message Modem to match

the standard DB-25 assignments in the following table. DB-9

connectors for IBM/AT-compatible computers should be wired at the

computer end of the cable as shown in the DB-9 column.

Serial Interface Pin Definitions

Signal Source

DB-25DB-9 Circuit Function Computer/Modem

1 — AA Chassis Ground Both

2 3 BA Transmitted Data Computer

3 2 BB Received Data Modem

4 7 CA Request to Send Computer

5 8 CB Clear to Send Modem

6 6 CC Data Set Ready Modem

7 5 AB Signal Ground Both

8 1 CF Carrier Detect Modem

12 — SCF Speed Indicate Modem

20 4 CD Data Terminal Ready Computer

22 9 CE Ring Indicate Modem

1 2 ... 67 68 69 70 71 72 73 74 75

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US Robotics 56K MESSAGE MODEM - QUICK FOR WINDOWS Podręcznik Użytkownika Strona 72