| 摘要 |
Second slave unit (4) transmits a downlink current signal by changing an electric current flowing in from a pair of electrical wires (51, 52). Resistor (22) in master unit (2) is provided between voltage applicator (21) and a pair of electrical wires (51, 52) and limits an electric current that flows through a pair of electrical wires (51, 52) when the pair of electrical wires (51, 52) is short-circuited by first slave unit (3). Receiver (23) in master unit (2) receives a downlink voltage signal resulting from conversion of the downlink current signal into a change in voltage in the pair of electrical wires (51, 52) by a voltage drop at resistor (22). |
