PURPOSE: To control a transistor (TR) for driving a buzzer, to select the best alarm sound pressure for an in-use atmosphere, and to obtain time information securely, by providing plural predriver circuits having different output currents and operating them selectively.

CONSTITUTION: The output of an oscillating circuit 1 is transmitted as time data to a display driving circuit 3 through a frequency dividing circuit 2 to operate a display 4. Data for alarm generation, on the other hand, is inputted from a switch 5 and a buzzer 10 generates an alarm sound by circuits 7W9. Alarm sound pressure level information is displayed on the display 4 under the control of a control circuit 6. In this case, one of clocked inverters 8aW8e of the predriver circuit 8 is selected during the generation of the alarm sound through the output lines (a)W(e) of the control circuit 6 and data lines for displaying the sound pressure level are used simultaneously to supply a signal to the display driving circuit 3.