| 摘要 |
PURPOSE: To continue an operation at a non-changing frequency even after a reference frequency fails in an inexpensive switching circuit by supplying a phase control loop for changing the characteristic line of a voltage controlled oscillator by a replacing clock switching circuit. CONSTITUTION: In the case that a transistor TR T2 is switched, the output voltage of a nominal voltage generator SG is applied to the input of an oscillator OS. By adjusting resistors R2 and R3, the voltage can be selected so as to make the oscillator OS oscillate at a prescribed frequency. Two voltage controllers R7, R9 and R8 and R10 are activated by the input so as to hardly change the frequency within the time when the replacing clock switching circuit is active. Thus, the switching of the TR T2 simultaneously reduces the sensitivity of the oscillator OS. Activation is executed by the TR T3 connected to the output of a comparator VG2 through the resistor R11 and two voltage dividers R7 and R8 are provided as the result of the specified deformation of the oscillator OS. |
