PURPOSE: To detect a breakage of glass and the intrusion into an automobile with high reliability without opening a door by detecting a sound, a vibration and a movement within the automobile.

CONSTITUTION: A safety sensor system is formed of three sensors of a sound detecting circuit 100 for detecting the acoustic energy within an automobile, a vibration detecting circuit 122 for monitoring vibration, and a detecting circuit 134 for detecting a movement within the automobile. The circuit 100 comprises a microphone, and it detects an important sound level within the automobile, particularly, glass breakage, and transmits a detection signal to a processor 118. The processor 118 gives a glass breakage alarm to a peripheral safety system 168 on the basis of the detection signal to flash an alarm 170, for example, a flash light, and also drives the circuit 134 to detect the intrusion into the automobile by microwave. Even when a pet or the like is left within the automobile, no movement is detected until the alarm is given.