I was thinking about the dispatch center. When I worked on software for the LAPD ECCCS system in the 80s, timing was established by the OS timing (rsx-11m) external sync was by wristwatch. I doubt it's any more precise now. They would get a feed from the E911 system. So the tight timing to get caller location would be in that system, not the PD's system. The dispatch system needed millisecond response time ( for radio voice switching) but not absolute timing. It ran with a hot standby for fail over and used dual port disk drives. The file system (my part) used OS timestamps.
Sent via the Samsung Galaxy S®6 active, an AT&T 4G LTE smartphone-------- Original message --------From: Magnus Danielson <mag...@rubidium.dyndns.org> Date: 2/27/2016 10:54 AM (GMT-08:00) To: time-nuts@febo.com Cc: mag...@rubidium.se Subject: Re: [time-nuts] GPS Outage.. Hi Jim, On 02/27/2016 06:14 PM, jimlux wrote: > On 2/26/16 11:34 PM, Hal Murray wrote: >>>> How many of them came from E-911 stations? >>> E-911 triangulation done on cell towers … >> >> I was thinking of the stations where they have the dispatchers who >> answer the >> calls >> and pass the info on to the right people. I think they need good >> timing on >> the recordings, but don't know any details. I've always thought some >> of them >> used GPS. >> > > > They need good time, but probably only to the nearest second. Phase alignment is relevant for TDMA based systems as well as CDMA based systems, but for a bit different reasons. GSM for instance actually have phase requirements, but dodges it by using one of many options to compensate the phase difference between different towers. Cheers, Magnus _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
