| 摘要 |
PURPOSE:To protect a magnetic recording medium by providing a magnetic sensor element whose electrical resistance or optical crystal structure varies with an magnetic field from outside and an alarm-sound output device to easily detect the said magnetic field generated from a concealed material. CONSTITUTION:In the magnetic sensor 1, an electric current in conducted through, for instance, an indium-antimony thin film whose electrical resistance varies by an external magnetic field, and its output is inputted to one input terminal of a comparator 2. To the other input terminal of the comparator 2, a reference voltage is impressed. An output from the comparator 2 goes through a switch 3 which controls the alarm-sound generating device 4, and the output is inputted to a speaker 5. A switch 6 is attached to the device 4. Since the existence of an invisible magnetism is detected and alarmed as a sound, a person who deals with an item to which magnetism is a harm such as a floppy disc, etc., can notice the presence of magnetism by carrying this device with him or her, accordingly such a place can be avoided. |
