Re: RS485 is bidirectional does it mean it is fullduplex?

Floyd L. Davidson wrote:

> However, if the cable is a long run, and particularly if there
> is exposure to power lines, if the ground potential is different
> at the two ends, or if there are any other sources of induced
> noise in the cable, this arrangement has the best effect:
>
> +-------+ +-------+
> | | >--------- tx wire/pair ---------> | |
> | EQUIP | <--------- rx wire/pair ---------< | EQUIP |
> | | ========= cable shield ========= | |
> +-------+ | | +-------+
> | | | |
> | | | |
> o------+ +------o
> | |
> ----- Earth ----- Earth
> --- Ground --- Ground

If you really do need to connect at both ends then you may need to consider
inserting some impedance in the screen connections at both ends (usually a
capacitor and resistor in parallel). The resistor is large enough to
prevent high current flows but needs to be small enough to provide an
effective electrostatic drain. The capacitor provides a low impedance at
higher frequencies.

--
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