Posted on Feb 6, 2014

In this card there is a constant current source is used to activate the phone. The LM339 is used to detect out of hand and the hand of the condition. There are circuits repeat the same because we have the phone interface 8. When the phone on hand in the output of the LM339 change is detected by the microcontroller that the phone is in the area, th

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en make the microcontroller is using the MT8816 analog channel. the LM555 is used to generate a dial tone.

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