| 摘要 |
1,103,515. Automatic frequency control systems. COMPAGME FBANCAISE THOMSON HOUSTON-HOTCHKISS BRANDT. 5 Nov., 1965 [12 Nov., 1964], No. 47130/65. Heading H3A. In a circuit for synchronizing a local clock with received sync. pulses in a digital transmission system, the sync. pulses are passed to first and second circuits, each fed by pulses derived from the clock pulses. In the first circuit it is determined whether there is one sync. pulse only in the period t between two clock pulses and for each of these a pulse passes to a logic arrangement. If there is more than a certain number of adjacent periods t when one pulse is present another pulse is passed to the logic arrangement. The second circuit is similar in operation to the first except that the period of inspection is t/4, centred on the mid-point of period t. From the signals passed to the logical arrangement are generated pulses whose width is dependent on the difference in phase of the clock and sync. pulses, and which are used to develop a voltage for the control of the phase of the clock generator. Details of the various circuits are given in the Specification. |
