T ECHNICAL Q UICK REFERENCE172The Serial InterfaceThe serial interface is a standard developed by the Electronic Industries Association(EIA). It defines the signals and voltages used when data is exchanged between acomputer and a modem or serial printer.The entire standard covers many more functions than are used in most datacommunications applications. Data is transmitted between the devices over a shieldedserial cable with a 25-pin male (DB-25) connector to the modem and a 25-pin, 9-pin, 8-pin, or custom-built connector to the computer.FCC regulations require the use of a shielded cable when connecting a modem to acomputer to ensure minimal interference with radio and television.Pin assignments are factory-set in the Sportster modem to match the standard DB-25assignments in the following table. DB-9 connectors for IBM/AT-compatiblecomputers should be wired at the computer end of the cable as shown in the DB-9column.
