| 摘要 |
<P>PROBLEM TO BE SOLVED: To decide the frequency shift of a reference oscillator itself inside a device without using an oscillator for measurement, to specify a frequency abnormal part and to prevent the transmission of an abnormal frequency clock relating to a system clock supplier and a frequency shift deciding method of the reference oscillator. <P>SOLUTION: The output clock of the reference oscillators (#N, #E) 9-1 such as OCXOs respectively provided inside the system clock supplier of duplex constitution (N system and E system) and a reference clock (8KHz, for instance) normally inputted for system synchronization are respectively compared in frequency shift measurement parts (#N, #E) 1-1, and the occurrence of the frequency shift for the prescribed number of times is measured in erroneous detection protective circuits (#N, #E) 1-2. On the basis of the measured results of both systems, the frequency shift of the output clock of the reference oscillator (#N, #E) 9-1 of the present system or the other system or the abnormality of the reference clock is decided and the abnormal part is specified in abnormal part deciding parts (#N, #E) 1-3, and selection signals are transmitted so as to switch the abnormal part to the other system. <P>COPYRIGHT: (C)2008,JPO&INPIT |
