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The telex network is a switched network of teleprinters similar to a telephone network, for the purposes of sending text-based messages. The term refers to the network, not the teleprinters; point-to-point teleprinter systems had been in use long before telex exchanges were formed starting in the 1930s. Teleprinters evolved from telegraph systems, and like the telegraph they used the presence or absence of a pre-defined level of current to represent the mark or space symbols. This is as opposed to the analog telephone system, which used differing voltages to encode frequency information. For this reason, telex exchanges were entirely separate from the telephone system, with their own signalling standards, exchanges and system of "telex numbers" (the counterpart of a telephone number). When telephone and telex exchange equipment was co-located, which was not uncommon, the different signalling systems would sometimes cause interference. Telex provided the first common medium for international record communications using standard signalling techniques and operating criteria as specified by the International Telecommunication Union. Customers on any telex exchange could deliver messages to any other, around the world. To lower line usage, telex messages were normally first encoded onto paper tape and then read into the line as quickly as possible. The system normally delivered information at 50 baud or approximately 66 words per minute encoded using the International Telegraph Alphabet No. 2. In the late days of the telex networks, end-user equipment was often replaced by modems and phone lines as well, reducing the telex network to what was effectively a directory service running on the phone network. ==Development== Telex began in Germany as a research and development program in 1926 that became an operational teleprinter service in 1933. The service was operated by the ''Reichspost'' (Reich postal service) and had a speed of 50 baud — approximately 66 words-per-minute. Telex spread around the world very rapidly. By 1978, West Germany and West Berlin together had 123,298 telex connections. Long before automatic telephony was available, most countries, even in central Africa and Asia, had at least a few high-frequency (shortwave) telex links. Often these radio links were first established by government postal and telegraph services (PTTs). The most common radio standard, CCITT R.44 had error-corrected retransmitting time-division multiplexing of radio channels. Most impoverished PTTs operated their telex-on-radio (TOR) channels non-stop, to get the maximum value from them. The cost of TOR equipment has continued to fall. Although initially specialised equipment was required, many amateur radio operators now operate TOR (also known as RTTY) with special software and inexpensive hardware to adapt computer sound cards to short-wave radios.〔(【引用サイトリンク】title=RTTY Software )〕 Modern “cablegrams” or “telegrams” actually operate over dedicated telex networks, using TOR whenever required. Telex was the forerunner of modern fax, email, and texting. Abbreviated English (like: CU L8R for ‘see you later’) used in texting was first used by telex operators exchanging informal messages in real time — they were the first ‘texters’ long before mobile phones. Telex users could send the same message to several places around the world at the same time, like email today, using the Western Union InfoMaster Computer. This involved transmitting the message via paper tape to the InfoMaster Computer (dial code 6111) and specifying the destination addresses for the single text. In this way, a single message could be sent to multiple distant Telex and TWX machines as well as delivering the same message to non-Telex and non-TWX subscribers via Western Union Mailgram. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Telex」の詳細全文を読む スポンサード リンク
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