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The radio constructor "Start 7239" (Loudspeaker Protection Device) since 1988 was manufactured by the Kamenets-Podolsk plant "Elektropribor". The radio constructor allows you to assemble a speaker protection device designed to turn off the power supply of the PA with bipolar power when a constant voltage appears at the output of one amplifier channel due to failure of the output transistors, blocks the power supply when one of the polarities is absent, and additionally removes clicks in the speakers at the moment of switching power supply. Powered by the power supply unit power amplifier. Supply voltage ± 25 ... 30 V. The dimensions of the device are 167x92x45 mm. Its weight is 200 grams.
Based on information from collection of Valery Khartchenko