PURPOSE: To increase the time resolution of a system, by using a leading edge discriminator and a comparator and compensating the time work for the output signal of a semiconductor detector, etc.

CONSTITUTION: The output signals 1 and 2 of a radiation detector are supplied to a leading edge discriminator 22, an attenuator 23 and a delay line 24 respectively. The discriminator 22 produces timing pulses 25 and 26. These pulses contain time works T3 and T4 respectively. The signals 27 and 28 are delivered from the attenuator 23 to be added 29 with the signals 25 and 26. The added signals 31 and 32 are compared 35 with the delayed signals 33 and 34 given from the line 24. Thus a timing pulse 37 having the compensated time work is obtained at an output terminal 36.