PURPOSE: To provide a digital voice switch incorporating type signal processor capable of substantially realizing low power consumption by controlling the power consumption of the signal processor corresponding to the state of a signal inputted to the processor.

CONSTITUTION: This processor is provided with a sequencer circuit 39 which detects the presence/absence of a sound signal 3E by which signal processing is performed, a PLL 34 which changes an instruction cycle supplied to the signal processor 30 corresponding to the presence/absence of the sound signal, and a clock generation part 35. When the sound signal 3E is inputted to the signal processor 30, the 'presence' of the sound signal is detected by the sequencer circuit 39, and the instruction cycle in this case is supplied to the signal processor 30 by the PLL 34 and the clock generating part 35. Also, when the 'absence' of the sound signal is detected by the sequencer circuit 39, the instruction cycle lower than that in the case of 'presence' of the sound signal is supplied to the signal processor by the circuit, thereby, the power consumption can be reduced.