"Greg Mayman" wrote to "Mike Ross" (04 Jan 03  08:37:00)
 --- on the topic of "LIGHTNING STRIKE"

 GM> I've seen the effect of induced voltage in telephone lines due to
 GM> nearby lightning strikes -- NOT direct hits! -- that sparked
 GM> across gaps of an inch or more. 1488/89s wouldn't give much
 GM> protection against that.

 GM> OTOH, if its only a few hundred volts, enough to kill an IC but
 GM> not enough to jump all over a board, then those 1488/89 chips
 GM> would offer a lot of protection.

Sure, HV will get by but the point of the 1488/89 ic's is that they have
relatively large value resistors in-line with the signal and these tend
to absorb a lot of grief from whatever is connected to the ic. I didn't
mean the ic would survive indefinetly but if the cleaning lady goes by
with a vacuum cleaner and induces a nice little static spark into the
phone line then the 1488/89's series resistors will mitigate the damage
on a regular basis and none is the wiser.


 GM> I still prefer an external modem. It puts several more ICs and
 GM> some solid physical separation between the phone line and the
 GM> motherboard ;-)

Not to mention more grounding opportunities for glitches to jump to.


 GM> And I prefer external modems for another completely separate
 GM> reason -- AFAIK they don't yet make them Plug-N-Play, which means
 GM> I can still use them with DOS 

Yes, I don't see the point either of stealing cpu cycles to run a modem.
Heck most of the cost of a modem is in the packaging not the circuit!

 Mike
 ****

... Now touch these wires to your tongue!
--- Blue Wave/DOS v2.30