sequential (-7)

https://wodewangzhishime.blogspot.com/2022/03/httpswodewangzhishime_1.html

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Ref: https://wodewangzhishime.blogspot.com/2021/07/httpswodewangzhishime_76.html

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Me: R0 ,R1, R2 are the physical address of the radio receivers. .
John: The more far from the radio emitter, the weaker the signal. . Ok. The distance between radio emitter and R1 or R2 are samely 2 meters. Why R1's signal is much weaker than R2??

Me: Because, R1 is at 45 degree of angle. On the contrary, R2 is at 90 degree of angle.
John: Ok. R1 and R0 have same signal's weakness  . How do I know where they are located ??.

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The emitter send a signal to R0 and R1, and , wait until they echo.
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1) R0 need 3 second to echo. R0 is more far from the radio emittor.
2) R1 need 1 second to echo. R1 is more near the radio emittor.