I've participated in many a design meeting debating the size of battery backup to provide a cell sites. The number usually settled upon ranges between 30 minutes and 2 hours. If it's an inside-the-building reinforcement site, it might have 15 minutes of battery reserve, or sometimes zero. The idea is to provide for normal type outages, not systemic power failures. The switching centers, of course, have large battery reserves (8 hours is common) plus a generator as a local power failure would other place at risk the entire network. It's been a very long time since I've seen a cellular system designed for extended battery operation at all cell sites; the economics just won't support it. Early in the life of cellular (mid 1980's), base stations were large; it wasn't uncommon to have a 1,000 square foot building with both battery power and diesel or natural gas generators and racks of equipment inside the building. Typical coverage was 6-10 miles or even more. You may have only needed a couple dozen to cover a large metropolitan area. It wasn't uncommon to have a couple million dollars of building, electronics, tower and power at one of those sites, particularly if it was shared amongst several operators. In that case, backup power only added a modest increment cost to the total network. Now, base stations are the size of a small refrigerator and coverage ranges are often a thousand feet or so in urban areas. Outdoor weatherproof enclosures have replaced stand-alone shelters. And these mini and micro base stations cost in the range of ten thousands dollars or a bit more. You can't cost justify an 8 hour battery plant at each of 500-750 base stations in an area the size of New York City, as desirable as it might turn out to be once every 25 years. (Last NYC blackout was 1977.) Jack -----Original Message----- From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of R Prosser Sent: Thursday, August 14, 2003 6:36 PM To: PICLIST@MITVMA.MIT.EDU Subject: Re: [EE]: Blackout Here in NZ, most (All?) cell sites have battery backup. (That's part of our income!) but the system depends on communication to the main call centres. If you are calling your next door neighbour (or closer), the call is still routed through the call centre which is likely to be in a different city! Therefore, in a major emergency, with fibre optic cables cut & microwave towers misaligned, both cellphone & trunk landlines are likely to be affected. I believe this holds for AMPS, GSM & CDMA systems. RP Uh oh. The fine print says that Cell phone service is knocked out by ......snip -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu --- Incoming mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.509 / Virus Database: 306 - Release Date: 8/12/2003 --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.509 / Virus Database: 306 - Release Date: 8/12/2003 -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu