Do cellphones get the time via atomic clock signal (WWV) or GPS satellite signal?
As everyone knows, cellphones set themselves and keep very accurate time. However, I’m still not sure HOW they get the time in the first place.
I always thought cellphones picked up on the time signal broadcast by the atomic clock (WWV radio station) in Colorado, or a similar atomic clock elsewhere (for those not in the U.S.) But someone else recently suggested to me that cellphones used a signal being broadcast from a GPS satellite (or more than one; I don’t actually know how many GPS satellites there are).
Does anyone know conclusively whether cellphones set themselves by the atomic clock, or by GPS satellite? Thank you.
Cell phones have had downloaded time since digital phones service started. Prior to that you had to set it. Digital service started before phones had GPS access. The time is set by the service provider. They probably receive their time from WWV.
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February 7th, 2010 at 4:31 pm
I’m not certain about this, but my understanding is that cell phones typically get the time from the network they are on – say Verizon/AT&T. Or at least get periodical updates from the network they are on. They do not get it from either the GPS satellite or the WWV radio
For some technologies, like CDMA, there is a fairly tight correlation between time and the technology, so for those phones, getting the correct time is a lucky side-effect.
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February 7th, 2010 at 4:47 pm
Cell phones have had downloaded time since digital phones service started. Prior to that you had to set it. Digital service started before phones had GPS access. The time is set by the service provider. They probably receive their time from WWV.
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