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Synchronous transmit-receive (STR) was an early IBM character-oriented communications protocol which preceded Bisync. STR was point-to-point only, and employed a ''four-of-eight'' transmission code, communicating at up to 5100 characters per second over half-duplex or full-duplex communication lines. The IBM 1009 Data Transmission Unit, the IBM 1130 Synchronous Communications Adapter, the IBM System/360 model 20 Communications Adapter, and the IBM 2701 Data Transmission Unit provided host computer support for STR. The IBM 7701, the IBM 7702 Magnetic Tape Transmission Terminal, the IBM 1013 Card Transmission Terminal, and the IBM 7710 and IBM 7711 Data Communication Units were among the remote devices supported by STR. STR was still supported as of 1972,〔 although it had generally faded from use. ==Four-of-eight code== The four-of-eight code was a 64 character set plus six control characters, encoded in eight bits. Exactly four bits of each character were one bits — there are 70 such possible bit combinations. 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「Synchronous transmit-receive」の詳細全文を読む スポンサード リンク
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