Teletypewriter Exchange Systems

After a connection has been established, the two parties type messages back and forth, with the decided advantage that typed copies of all transactions are available to both parties. Payment is made on a time basis. This service was established by the Bell System in 1931. Leased Wire Service. Large industries, the press, public agencies, and other organizations, such as financial houses, are provided with leased-wire telegraph service by both the Bell System and Western Union. These circuits are usually terminated in printing telegraph equipment and may extend between offices and plants, branch offices, etc.

Leased channels may be set up for long periods or may be of such nature that occasional switching is necessary. Special apparatus, often designed on a customer basis, is available for this purpose.^15,16 The varioplex system, described earlier in this chapter, and telegraph concentrators^2,16 are useful in providing the occasional transmission needed by TWX and leased-wire customers.