| 摘要 |
PURPOSE:To ensure the high reliability of an analog data transmission line through automatic line changeover by using analog data from a channel section of a carrier terminal equipment to supervise always a transmission line thereby making the maintenance and inspection effective. CONSTITUTION:A data modulator-demodulator 202 converts base band data 201 into a data signal 203 in a voice band and the result is fed to an automatic line changeover device 204. A band stop filter 205 of the device 204 eliminates the component of a pilot signal of the signal 203 and branches the result into two, which are combined with a pilot signal from a pilot signal generator 206 at each of combiners 208, 209 and the combined result is transmitted to existing and spare carrier lines 212, 213. The signal 203 and the pilot signal from the lines 212, 213 are received by existing and spare separators 217, 218 of the automatic line changeover device 216 and the result is fed to a changeover device 221 and BPF219, 220. The pilot signal extracted from the BPF219, 220 is supervised by pilot supervisory circuit 223, 224 and the output controls the switch 221 thereby improving the reliability of changeover.
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