>When does the transmission line effect become an actual concern, what =
type
>of data transfer, is it more of an outgoing than incoming thing, or =
more of
>a high speed than a low speed issue?

it becomes a problem when the length of wire becomes a receiving aerial =
for any R/T, taxi radio, cellphone, FM Broadcast station, Radar =
transmitter, or any other source of mildly strong EMF that gets =
rectified in some stray diode in your input circuitry. Normal trick is =
to use some form of series resistor/capacitor on the input pin, say =
1kohm/1nF to filter any such junk.

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
"[PIC]:" PIC only "[EE]:" engineering "[OT]:" off topic "[AD]:" ad's