PURPOSE: To form an inexpensive home security device which is free from malfunction by providing a timer circuit which outputs a gas detecting signal upon discriminating that the output of a comparator comparing the output of a gas sensor with a specific reference level continues for more than prescribed time.

CONSTITUTION: This invention is to form a home security device having a noise-free gas leakage detecting and robbery preventing functions by using the timer circuit 3 or delay circuits 6, 8, and 10. The gas sensor 1 is connected with a preferential circuit 4 through the comparator 2 for detecting level and the timer circuit 3 for counting time for 30 seconds. In addition, a fire sensor 5 constituted of a heat-sensitive device, emergency sensor 7 for reporting emergency, and robbery preventing sensor 9 which detects the opening and closing of doors and windows are connected with the above-mentioned preferential circuit 4 respectively through the delay circuits 6, 8, and 10. Since the hardware- constituted timer circuit 3 and delay circuits 6, 8, and 10 are used, this home security device can be used more effectively and inexpensively as compared with a similar device using a microcomputer.