PURPOSE: To enable reduction in load on a processing system, especially, priority processing such as processing of an important call during abnormal convergence and disconnection and response processing, by prescribing the priority level of input data at a processor side by a queue number.

CONSTITUTION: A register input is inputted to memory 2 via signal line 1 and further written in memory 6 through processor 5. According to the kind of the input signal and the kind of a change, signal processor 5 adds the detection signal of the register input change to each corresponding queue 7 successively. The output signal of main processor 9 is converted by decoder 8 into the read signal of each queue 7 and data is read out of each queue 7. This read data is supplied to main processor 9 via selector 10. With this data, main processor 9 performs data processing. Then, using different scanning periods gives a read of each queue 7 a priority level.