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Text excerpt from page 23 (click to view)
5. OCP (OVER CURRENT PROTECTION) CIRCUIT
This circuit is designed to protect the circuit from over current due to overload occurred at the rear of 123[V] line 1) CONFIGURATION OF OCP CIRCUIT
2) EXPLANATION OF THE OPERATION There is very little voltage drop at R423 of 123[V] line. In case that the overload occurs at the rear of 123[V] line, the increase of the voltage drop at R423 bring down the base voltage of the Q407 os as to drive the Q407 Because of the overload at the rear of the R423, the voltage of the point decreases. And this makes Q407 turn on so that a voltage is applied to the #31 of l701. In case that OCP operates by the #31 of the l1701, the set is protected by power off (#42 of l1701 LOW).
