4
WIDE AREA NETWORK TRANSMISSION EQUIPMENT
One method of categorizing data communications components is by the function or group of functions they are designed to perform. In this chapter, the operation and utilization of networking devices designed primarily to provide data transmission via a wide area network communications medium will be covered. Specific devices which will be explored in this chapter include a variety of analog and digital transmission products that can be used to transmit data over analog or digital wide area network transmission facilities. Analog transmission devices covered in this chapter range in scope from the nearly obsolete acoustic coupler to a half-dozen types of modems, including state-of-the-art cable and digital subscriber line modems. Digital transmission devices covered in this chapter include different types of data and channel service units and a device that permits the extension of parallel transmission from a computer to peripheral units located at a distance from a computational facility.
4.1 ACOUSTIC COUPLERS
An acoustic coupler is in essence a modem which permits data transmission through the utilization of the handset of an ordinary telephone. Similar in functioning to a modem, an acoustic coupler is a device which will accept a serial asynchronous data stream from terminal devices, modulates that data stream into the audio spectrum, and then transmit the audio tones over a switched or dial-up telephone connection.
Acoustic couplers ...
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