| 摘要 |
4. Information transmission system, in particular for use in opencast mines, comprising a central station and local stations, connected by means of a single pair of wires or by radio through the inclusion of radiotelephones in the transmission path, characterized in that each station, whether central or local, has an identical structure and comprises a control component (SM) and, connected to it, a data transmission block (BTD), having at its input a receiving filter (1), whose input is connected to the transmission path (T) and whose output is connected to an amplifier-limiter (2), of which one output is connected to a frequency doubler (3), connected via a frequency discriminator (4), low-pass post-detection filter (5) and forming circuit (6) to one input (RXD) of the control component (SM), whose second input (DSR) is connected to the second output of the amplifier-limiter (2) via a level discriminator (7), while one output (TXD) of the control components (SM) is connected via a frequency modulator (8) and linear amplifier (9) to the signal input of a key (10), whose control input is connected to the second output (RTS) of the control component (SM), while its output is connected to the transmission path (T), and the frequency modulator (8) of the local station and the frequency discriminator (4) of the central station are tuned to a lower frequency than the frequency modulator (8) of the central station and the frequency discriminator (4) of the local station.<IMAGE>
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