| 摘要 |
The overload protection circuit for loudspeakers described generates a direct voltage by rectification of the amplifier output voltage, from which direct voltage an operating voltage for trigger circuits and an exciter voltage for a relay are derived, via the normally closed contact of which the amplifier output voltage is supplied directly to the loudspeaker to be protected in the normal case. A section of the direct voltage is supplied via a voltage divider to the trigger circuit as input voltage and when the amplifier output voltage reaches dangerous values, the trigger circuit is triggered and brings a switch transistor connected in series with the relay to the exciter voltage into the conducting state so that the relay operates. As a result, its normally closed contact is opened and the amplifier output voltage is transferred to a latching circuit for the relay via a normally open contact. This latching circuit simultaneously provides for a hysteresis characteristic so that the relay is only released when the amplifier output voltage has dropped again below the operating voltage of the protection circuit by a predetermined amount. <IMAGE>
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