| 摘要 |
Apparatus for mutually synchronizing central office clock oscillators provided in each of a plurality of interconnected switching centers of a telecommunication network is described. In each switching center the local clock oscillator output is coupled to a central office frequency divider, while the clock signals from other switching centers are coupled to line frequency dividers. After the occurrence of each reference phase formation, the line frequency dividers operate 180 DEG out of phase with the central office frequency divider. Phase comparators are coupled to the outputs of each line frequency divider, as well as the output of the central office frequency divider for producing output signals indicative of the phase difference between the line frequencies and the local clock frequency. The outputs of the phase comparators are resistively added producing a mean signal, which regulate the local clock oscillator. The control range of the clock oscillator corresponds to the measured phase difference conditioned by the greatest possible no-load frequency difference between the compared switching centers' clock outputs. A reference phase formation occurs upon the crossing of this control range. A second synchronizing circuit is additionally provided and is constructed in the same manner as the above synchronizing circuit. This circuit has a control range corresponding to the phase difference resulting from the sum of the phase difference between switching centers and the greatest transit time on the multiplex lines connecting the compared switching centers. An additional control signal is supplied by this second synchronizing circuit for aiding in the regulation of the local clock oscillator.
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