| 摘要 |
1,146,873. Data transmission systems. TELEFUNKEN PATENTVERWERTUNGS G.m.b.H. 6 April, 1966 [6 April, 1965], No. 15303/66. Heading H4P. In a system in which digital data is transmitted in blocks, a return error/no error indicating signal being received prior to the transmission of each block, each block includes a multi-bit check word derived by a feedback shift register from the information data. A similar feedback register checks the received blocks. Co-operating stations are identical, their mode of operation at any time being selected by switches controlled by a control unit. At the transmitter the bits transmitted are counted, and after a given number the control unit reads out the check word developed in the register, following which the transmitter is switched to receive. At the receiver a counter fed by the received bits operates the control unit so that only the information bits are passed to the output. The complete block is passed to the register which also feeds the control unit. When a complete block has been counted the control unit passes the output of the register, which indicates whether or not an error has occurred, to a unit which develops an error/no error signal which is returned to the transmitter over the same line as that on which the block was received. This signal passes to the shift register there and, depending on the bit-pattern, causes the transmitter to be switched back to transmission and either to repeat the previous block or to send the next block. If the transmitter receives no signal from the line during a preset period it generates a service signal. It may be arranged that a station acting as receiver may, by sending a special service signal, act as a transmitter of data blocks. A plurality of stations may be interconnected, each station responding only to a particular service signal. A single station may broadcast to a plurality of receivers: in this case only one of the receivers returns an error/no error signal. The other stations each derive an error/no error signal and compare it with that returned by the receiver. If lack of agreement is found by one of these stations it sends a special service signal. |
