| 摘要 |
PROBLEM TO BE SOLVED: To securely detect the opening of a casing in a device storing security information on CAT etc. SOLUTION: A light emitting diode 7 and a light receiving phototransistor 5 are installed respectively in the casings 1a and 1b of terminal equipment which is vertically divided into two. The light emitting diode 7 and the light receiving phototransistor 5 are irregularly driven. The output of the light emitting diode 7 is changed and the threshold of the light receiving level of the light receiving phototransistor 5 is changed accordingly. The light receiving phototransistor 5 sometimes detects disturbance light. The light receiving phototransistor 5 monitors the light receiving level of light from the light receiving diode 7 and the light receiving level by diffused external light. When the levels are abnormal, the casing 1a is detected to be opened and it is informed to a high-order device through a public line. |
