Re: Offtopic: Re: DE and hot-swap disk caddies

Martin Dalecki
2002-03-28T09:55:48Z

Jos Hulzink wrote:
> On Thu, 28 Mar 2002, Alan Cox wrote:
>
>
>>>Then there is this talking around about the "tristate of some" device.
>>>I'm really a bit sick of it. Becouse there is no such a state
>>>like a tri-state. We have just bus drivers on both ends.
>>>They are implemented usually as Schmidt triggers. They have three
>>>possible states on output: low voltage, high voltage, high resistance.
>>
>>Which is one, two, three states -> tri-state.
>
>
> Eeks, a Linux developper who can count ;-)
>
>
>>Electronics terminology then abuses that to mean the high impedance state (not
>>high resistance please if we are going to be picky).
>
>
> Correct, though I hope in most cases the impedance is almost equal to the
> resistance, otherwise there would be problems at the current high speeds.
>
> For those who don't know the difference:
>
> Resistance is only a part of impedance. Inpedance also contains a
> frequency-dependant part, caused by induction in, and capacity between
> wires and electronic devices.
>
> The idea in formula:
>
> Induction = Resistance +
> frequency * Induction +
> 1 / (frequency * Capacity)
>
> For an accurate formula, see any book about EE.

Ehmmm... it was a just too direct translation of the german term hochohmig ;-).
And indeed the correct english term is high-impedance.