| 单词 | telex ( teletypewriter exchange) |
| 释义 | telex ( teletypewriter exchange) Beginning in about 1910, telegraph companies began to use telex, a rotary dialing system for routing telegraph calls, much like that used in telephone networks.Telex initially ran at the amazing signaling speed of 45.5 bits per second (bps) and, later, at 50 bps, or 66 words per minute (wpm). At that signaling rate, one analog voice grade channel could support 24 or 25 telex transmissions through frequency division multiplexing (FDM). In 1958,Western Union introduced its Telex® service, a direct-dial consumer-to-consumer teleprinter service. In 1930, AT&T released its TWX (TeletypeWriter eXchange) service, a high speed telex service that ran at 75 bps, and later 150 bps. Western Union operated the TWX service in the United States for many years until AT&T acquired Western Union’s Telex network in 1990.Telex services eventually reached some 190 countries and 3.5 million machines, by some estimates.Telex was the first true electronic mail service and is still in use, largely in developing countries. Telex and TWX were used in business extensively at least in part because the networks provided the equivalent of caller ID, as each user was attached to a known port on a switch. This gave transmissions the property of nonrepudiation. See also AT&T, FDM, telegraph, voice grade, and Western Union. |
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