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- Path: sparky!uunet!pipex!bnr.co.uk!uknet!strath-cs!nntphost!jim
- From: jim@cs.strath.ac.uk (Jim Reid)
- Newsgroups: comp.protocols.time.ntp
- Subject: Re: Wireless time services -- standards?
- Message-ID: <JIM.93Jan5183518@hunter.cs.strath.ac.uk>
- Date: 5 Jan 93 18:35:18 GMT
- References: <tih.725986398@barsoom>
- Sender: news@cs.strath.ac.uk
- Organization: Computer Science Dept., Strathclyde Univ., Glasgow, Scotland.
- Lines: 53
- Nntp-Posting-Host: hunter.cs.strath.ac.uk
- In-reply-to: tih@barsoom.nhh.no's message of 2 Jan 93 14:53:18 GMT
-
- In article <tih.725986398@barsoom> tih@barsoom.nhh.no (Tom Ivar Helbekkmo) writes:
-
- Of course, one could argue that the VCR ought to have a battery backup
- for its clock, but I've got one of the cheaper models, and of course
- this is a feature that they reserve for people who can shell out
- bigger bucks for the thing than I can.
-
- Backup power supplies - usually big capacitors rather than batteries -
- for clocks on things like VCRs are very cheap: perhaps costing a few
- pennies.
-
- However, I got to thinking about this: Why the heck doesn't my VCR
- automatically find out what the current time is? Why doesn't my clock
- radio and other appliances that have clocks do the same thing?
-
- A good question, but the answer is simple: cost. A backup power supply
- for the clock is at least a couple of orders of magnitude cheaper than
- a decent radio clock receiver or a teletext decoder. Another problem
- is the diversity of time signals in the world: which one should the
- VCR manufacturer include? WWV? DCF? MSF? OMEGA? GPS? (The last two are
- probably best for availability throughout the world. However, they
- ain't cheap. The cheapest GPS clocks cost $5-600 - roughly twice that
- of a VCR.)
-
- It seems to me that something essential is missing here... There are
- radio stations and TV stations all over the place, transmitting a lot
- of stuff on different channels at the same time, so why don't we
- already have a standard for time information transmittal that these
- appliances can utilize?
-
- Probably because it's simpler and cheaper to put a quartz oscillator
- on the device. There are so many world-wide clock and broadcast
- standards that adding this feature to a VCR (say) would be a difficult
- technical and political problem. It would also add expense and
- complexity which could make sales harder to come by.
-
- And even without a general time broadcast system, the following could
- be done: Since a VCR has a TV receiver, there ought to be info
- contained within the normal TV broadcast signal telling the current
- time (probably specified as UTC, with the local time zone switch
- settable on the VCR), so that the VCR can keep its internal clock
- running correctly.
-
- TV teletext services already do this (at least in the UK). However, it
- is up to the broadcaster to determine the accuracy of the teletext
- time information. Some may be less bothered about this than others - I
- have seen cable-supplied teletext with times minutes away from GMT. [UK
- broadcasters sync their teletext clocks to the UK MSF signal.] This
- would add extra complexity in the user interface to household gadgets
- that are already over-complicated. [eg - how do you tell the VCR what
- timezone it's in or which channel's teletext to believe?]
-
- Jim
-