Data transmission through the telephone network: protocols, pitfalls, and some examples

Invariably, the situation arises where it is desirable to transfer data from one computer to another, especially from small laboratory systems, word processors, or home computers to large mainframe computers. In many of these cases, there are no common storage media; home computers do not have 9-track tape drives and large mainframes do not have 5 1/4 in. floppy disk drives. Transmission of data through the telephone network is a viable method for data transfer, which is paradoxically both easier than many believe and more difficult than some may claim. One of the keys to successful data transmission is an understanding of telecommunications protocols, i.e., the rules governing intersystem communication through the telephone network. Some of the most common protocols allow exchanging ASCII-coded data at either 300 or 1200 baud. A variety of computer systems can be used, including IBM and DEC mainframes, a Wang word processor, an IBM PC-compatible microcomputer, and the Atari 800 microcomputer. A specific example is the use of the Atari 800 as an APL terminal, complete with the custom character set, standard ASCII text, and data transfer.