A great many data transfers these days involve converting analog signals to digital signals. In this way, your computer can communicate with digital data providers, such as websites and other Internet-related sources. Whether you realize it or not, the modem with which you connect to the Internet is constantly doing this sort of data transfer.
Such data transfer naturally take time and effort, which you might want your computer to spend on other tasks. Technology is available, however, to connect directly to the digital network that is otherwise passing your modem by. This technology can come in the form of a terminal adapter.
A terminal adapter enables communication between a computer and an Integrated Services Digital Network (ISDN) line. ISDN is the current hot technology transmitting digital voice and other data. The transmissions are sent over the same old copper phone lines that we are all used to, but the result is much higher quality and speed than the traditional analog transmissions. Using a terminal adapter, you can plug your PC into the digital data transfer network.
A terminal adapter is a bit like a modem, but it doesn't waste time converting analog and digital signals. The terminal adapter is much more passive, serving its function only by passing on digital signals. Think of it as an aqueduct: The ISDN line is the outlying communities, and your computer is Rome.
The terminal adapter might not perform the same function as a traditional modem, but it does share one important characteristic with that modem: it is a peripheral. Current computer technologies do not list terminal adapters as standard features. If you want to use a terminal adapter, you have to purchase it separately. Both internal and external models are available, with the external model connecting to the serial port or USB port on your computer. Devices that combine the functionality of modems and terminal adapters are available as well.