| 摘要 |
PURPOSE:To simply detect the disconnection of a speaker circuit by dispensing with a tone back circuit and moreover an actual signal blowing in a detecting method for disconnection of a speaker circuit which is used for many emergency guidance broadcasting processes including a dam discharging alarm. CONSTITUTION:Since, when an inspection switch is closed, electric current flows from an output transformer 1 to a voice coil 4 and further to the output transformer 1, a photocoupler 6 turns into an on-state. If any disconnection occurs in a circuit, the electric current does not flow as above mentioned, the photocoupler 6 therefore turns into an off-state, and the disconnection can be judged. |
