SUBSCRIBER PREMISES OPTICAL NETWORK UNIT

摘要

In an ONU (100), a first serial signal terminal (121) of an ONU functional block (120) is connected through switch circuits (170a, 170b) to a first serial IF block (142). A ground wire (162b) is branched so as to be connected to the switch circuits (170a, 170b). A voltage applied to the ground wire (162b) is used as a control signal. When the ground wire (162b) is connected to ground, the switch circuits (170a, 170b) are cut off, so that an access from the first serial IF block (142) is not permitted. When a predetermined voltage is applied to the ground wire (162b), the switch circuits (170a, 170b) are energized, so that an access from the first serial IF block (142) is permitted.