Slave unit for automatic fire alarm system and automatic fire alarm system using same

A transmission circuit (14) is electrically connected to a pair of electric wires (51, 52), to which a voltage is applied, and draws in a current as a pull-in current from the pair of electric wires (51, 52). A determination unit (161) determines an operating state, including two states, namely a fire alarm state for notifying the occurrence of a fire and an interlocking alarm state for causing another device to operate in an interlocked manner. When the determination result of the determination unit (161) indicates the fire alarm state, a control unit (162) adjusts the current value of the pull-in current to a predetermined fire alarm level in order to generate a fire alarm. When the determination result of the determination unit (161) indicates the interlocking alarm state, the control unit (162) adjusts the current value of the pull-in current to a predetermined interlocking alarm different from the fire alarm level in order to generate an interlocking alarm.