[Ti] Annoying hum

[Jeffrey K. Lew]

>Whenever I am on the telephone and touch the case of my Ti 667 II 
>(as when I am using the keyboard and my palms are on the palmrests), 
>the person I am talking to and I can both hear an annoying hum 
>coming through the phone. I have tried a different telephone and get 
>the same results. I never had this problem with previous 
>plastic-cased PowerBooks (180, 540, 5300, WS II).
>
>The hum goes away if I unplug the phone and just run it on its 
>backup battery, but this removes most of the phone's functionality. 
>It also goes away if I unplug the PowerBook, but this requires 
>endless charging and swapping of batteries while I am working at my 
>desk.
>
>By the way, the phone and PowerBook are plugged into two different 
>wall outlets.
>
>Any suggestions?
>
>David Brostoff
>

This has been going on since the Wallstreet computers, without 
needing to touch the case (they were plastic anyway). Unplugging the 
AC from the computer stopped the hum. It's some EMI or RF, because it 
happens on phones that do not have external power supplies and it 
goes away if there's some distance between the phone and the cables 
around the computer.

Jeff Lew
UCLA Atmospheric Sciences