Yes, I was guessing a brownout, however didn't notice any other problems on the non-UPS systems.. Was just wondering if anyone else had noticed something or if it was localised to my area. (seems to be localised) To answer Lindsays question the UPS was flicking on and off constantly.. Around once a second for about 5 minutes. The UPS tests fine and didn't fault at all.. It just kept cycling between battery and line supply. My flatmate has mentioned something in my computer room beeping previously.. Which must be a similar issue .. Maybe the UPS must be fairly sensative to voltage changes (hardly ever tripped at my last house, but this house trips a bit more often) And yes, I know about power networks, im currently based and Huntly Power station, now that is some impressive machinery. -----Original Message----- From: Chris O'Halloran [mailto:chris.ohalloran(a)maxnet.co.nz] Sent: Monday, 3 October 2005 5:38 p.m. To: wlug(a)list.waikato.ac.nz Subject: Re: [wlug] Weird power Gavin makes a good point in that it might have been an abnormal 11/22kV switching scenario which has resulted in a lower fault level locally. For this period, voltage fluctuations on the network might have been greater than usual when motors were started etc. Is there a sewage or water pumping station near? A factory? As Gavin pointed out, the voltage only has to drop below the threshold of the UPS before the UPS will kick in. And this may not have been noticeable in your household lights. My original reply was more discounting the idea that the signals power companies use to switch streetlights, hot water cylinders, tariff meters etc were affecting your UPS. These are typically in the order of 2-6% (200-400Hz, older systems 1500Hz) and generally not noticed. Happy to be proved wrong. If your UPS checks out fine and the batteries are okay, then your UPS was doing its job. The power networks aren't perfect and do need maintenance from time to time so it warrants protecting your computers etc.