| 摘要 |
<p>A fire alarm system is equipped with a terminating capacitor (CE) connected across the terminal (EL) of a pair of lines (L) to which fire detectors (DE) are connected and with cut-off means (Tr1, Tr2) for cutting off the power supply to the lines in the case of a line interruption test. Furtheron, a discharge means (Tr3) causes the terminating capacitor (CE) to discharge when the power supply to the lines (L) is interrupted, and a discrimination means (MPU) compares the voltage available on the lines before interrupting the power supply with the line voltage after a predetermined time and judges, by the difference of these two voltages, whether there is an open in the lines, or not. Thereby, false operation of the line interruption supervision is prevented, due to a fluctuation of the power supply voltage, and a line interruption is detected reliably, even in fire alarm system having very long lines and a great number of fire detectors connected thereto, by which the discharge voltage is decreased.</p> |
