On 2/17/2011 8:50 AM, Art Todesco wrote:
I have a computer and DSL modem tied to an old UPS (with new batteries).
When I have a power failure, the computer keeps right on ticking, but I
always have to restart the DSL modem. I've even restarted the modem
while running on the UPS and after its restart, all was fine. I am
assuming here that the switch over time is killing the modem. I looked
at the modem and its walwart. It says 12 VDC. I was wondering if putting
a few thousand micro farad cap across the 12 volt line might help.
Anyone have any experience with something like this?

The whole point of a UPS is to prevent the very issue you are
describing. There shouldn't be any "switch over time". Sounds like the
UPS has issues.