| 摘要 |
PURPOSE: To maintain the accuracy of a clock hold-over circuit and to make it possible to supply also a switching clock signal by the combiniation of a digital circuit and a local frequency source by preparing a part depending upon time and temperature and selecting the parameter of the part within a required allowable range. CONSTITUTION: A countable signal is supplied from a monitor 26 to a counter 45 through a line 43, and when the signal is an input reference clock signal 10, a compensation value valid for a local clock reference signal 36 is generated from the counter 45. When the signal 10 disappears or becomes an invalid value, a parallel load enable signal is supplied from the monitor 26 to the counter 45 through a line 44 and a value finally stored in a register 46 is supplied to the counter 45. The value is supplied to a frequency synthesizer 38 through a line 48, an output from the synthesizer 38 is applied to the output of a mixer 35 and a phase comparator 34 through a circuit point, an output 33 from the comparator 34 is supplied to a VCO 29 through a switch 30, and the phase of the output 33 is synchronized with that of the reference signal 36 in the VCO 29. |
