A modem, or modulator-demodulator, is a device that provides the computer with connectivity to a telephone line. A modem converts data from a digital signal to an analog signal that is compatible with a standard phone line. The modem at the receiving end demodulates the signal, which converts it back to digital. Modems may be installed internally  or attached externally to the computer using a phone line.
    A NIC must be installed for each device on a network. A NIC provides a network interface for each host. Different types of NICs are used for various device configurations. Notebook computers may have a built-in interface or use a PCMCIA card.  Desktop systems may use an internal network adapter , called a NIC, or an external network adapter  that connects to the network through a USB port.
Situations that require NIC installation include the following:
  • Installation of a NIC on a PC that does not already have one
  • Replacement of a malfunctioning or damaged NIC
  • Upgrade from a 10-Mbps NIC to a 10/100/1000-Mbps NIC
  • Change to a different type of NIC, such as wireless
  • Installation of a secondary, or backup, NIC for network security reasons
To perform the installation of a NIC or modem the following resources may be required:
  • Knowledge of how the adapter, jumpers, and plug-and-play software are configured
  • Availability of diagnostic tools
  • Ability to resolve hardware resource conflicts