The switch circuit with two normally open contacts and closed contacts

Published:2011/6/10 20:33:00 Author:qqtang | Keyword: switch circuit, normally open contacts, closed contacts | From:SeekIC

In the figure is the switch circuit with two normally open contacts and closed contacts, when the input signal is a low LEV 0 , the transistor TV is blocked, the LED GY2 and GY4 in the photoelectric couplers have no currents, and the light dependent triodes GG2 and GG4 are blocked, which is equal to the switch cutting off, we call them the normally open contact; however, when there are currents in GY1 and GY3, which makes GG1 and GG3 conducting, that is equal to switch closing, we call them the normally closed contact. When the input signals are high LEV 1 , the transistor VT is conducting.



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