| 摘要 |
<p>1,274,110. Electric selective signalling; data transmission. GENERAL ELECTRIC CO. 27 Aug., 1969 [3 Sept., 1968], No. 42742/69. Heading G4H. A system for transmitting digital data from a number of remote stations to a central station includes, in the central station, a device for sequentially interrogating the remote stations and in the remote stations a control device which, on receipt of a command signal from the central station, scans the digital data, transmits it to the central station and generates a signal signifying the end of the transmission which, when received at the central station, causes the next remote station in the sequence to be interrogated. In an embodiment the data in each remote station is divided into three groups which are scanned sequentially. The remote stations receive a signal from the central station which consists of a remote station address and a number of command, sync., and parity bits. The correct station responds by energizing its control device which causes the first group of data to be scanned under the control of a counter. When the first group of data has been scanned the control device emits signals consisting of a word signifying the end of the first data group transmission, the complement of the station address and a parity character. The control device then initiates the second data group scan and on completion emits a word to that effect. The final data group consists of a number of two state devices which are only scanned if any of them have undergone an unauthorized change since the last scan. The control then emits a word signifying the completion of the transmission. The central station includes a number of data display units e.g. printers or C.R.T.'s which are sequentially energized in synchronism with the remote station scan. The data is handled in the central and remote stations in parallel form and is transmitted in serial form. A three position switch is provided at the central station to modify the command emitted to allow the first data group only or the first and second groups only or all three to be scanned. All transmission include sync. and parity bits to enable the central and remote stations to remain in synchronism and to detect faults.</p> |
