A loudspeaker protective unit for protecting a loudspeaker device against an
excessive
input current includes a lamp connected in series with the loudspeaker unit. The
lamp is housed in a casing exhibiting light-sealing properties formed of an electrically
conductive material, and is sealed with a sealant exhibiting a predetermined electrical
conductivity. The spacing between lead lines of the lamp housed in the casing is
of a preset value. An inert gas is sealed within a main lamp body unit and a preset
voltage is applied to the main lamp body unit. When the voltage is applied across
the lead lines, an electrical discharge is produced to interrupt the current flowing
through the filament so as to prohibit a temperature rise in the lamp.
