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The medical call receiver circuit with lighting signals

2014-11-29 07:22  
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The medical call receiver circuit with lighting signals
The medical call receiver circuit with lighting signals
In the figure is a receiver that can avoid leaving out the sound of asking for help, in the daytime, only the receiver works and the lights automatically cut off. At night, the receiver and the lights can be sent out with the request of the patients. When the calling key is pressed, the primary stage of transformer X1 is also connected with the AC power supply at the same time, and after being rectified and filtered, the power supply of the second stage outputs a DC voltage which is delivered to the collecting electrode of VT1 by R1. If it is the daytime, due to the rays, LDR1 is in a low resistance, VT1 is conducting, and the collecting electrode is reduced to the earth connection.