Setting hardware connections
A modem has to be connected to the telephone system and to a power source.
Both internal and external modems use a modular phone cord, called an RJ-11 coupler. Usually, a new modem includes the coupler. If you have an older, four-pronged jack, you might also need an adapter to connect to your phone line.
If your office has digital, PBX, or multiline phones, you cannot connect a modem directly to the phone system. You need to either install a standard line or install a device that connects your modem to one of these systems. See your computer or telephone supplier for specialized solutions.
Internal modems are powered directly by the computer. External modems usually come with a power adapter, but are sometimes powered by the computer. Most portable modems for portable computers use batteries, although they often come with an adapter. Some are powered directly from the computer. Modems use different sizes and styles of adapters, so if you lose the adapter, get a new one from the modem or computer manufacturer. Refer to the manufacturer's documentation for additional information about the power requirements of your computer.
External serial modems connect to the computer with a serial cable, also called an RS-232 cable. If a cable is not provided with your modem, make sure you get one that fits both your computer's serial port and the modem's port.