| 摘要 |
In each control node connected to an optical multiplex transmission path, a light receiving portion operates due to supply of a power source and receives an optical signal from another control node. A mode changing-over portion alternately changes over a multiplex communication mode and a sleep mode every prescribed period of time. A light receiving power source control portion and a first switch have alternately repeated therein a power source supply time length corresponding substantially to the multiplex communication mode during which a power source is supplied and a power source non-supply time length corresponding substantially to the sleep mode during which no power source is supplied, and thereby produces a power source supply pulse signal in which the duty ratio between the power source supply time length and the power source non-supply time length is preset and supplies this power source supply pulse signal to the light receiving portion. When the mode changing-over portion changes over the mode of the control node from the sleep mode to the multiplex communication mode and the light receiving portion has received the light signal, the mode changing-over portion causes the multiplex communication mode to be maintained during a time period in which the light signal is being received, and the light reception control portion causes the power source to continue to be supplied to the light receiving portion during a time period in which the light signal is being received.
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