Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Karen W. on 27/11/2007 23:28:42
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Two people sitting next to each other on a couch? (*Smiles at Meg,* She made me think
of this question in the other thread!)
Each have a cell phone in hand. One say meg sends message to friend . Friend receives
message in 26 seconds. BUT in that 26 seconds How far down the fiber optic
did that message have to travel in order to reach her friend in 26 seconds! And does
wireless count or make a difference in the speed of which the text traveled down that
line [???] Does it travel faster or slower then the speed of light [???]
I wonder Please do tell? Did it just travel two feet or millions of feet and back
again [???]
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That depends how canny the mobile phone system is. Assuming the phones are on the same network and connected to the same recieving antenna (this may not always be true because in my house if you have a phone on the orange network you connect to a different receiver at one end of the living room from the other and so there's a spot in the middle where it could go either way) If the network is clever and knows it can send the signal to the phone already connected to that arial it doesn't have any distance to go but thats probably not true so the message has to go back via the fibre optics to one of the main routing exchanges and back again.
If the two phones are not on the same network it's got to go much further via the links between the two networks.
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I would think it unlikely that a network will ever transmit directly from one phone to another, or not even simply mediated by the local repeater, since I suspect this would cause problems in charging (and providers may also log texts for availability for police, which means it has to get to a local computer).
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So really we are talking many many miles in most cases depending on where the provider is located and your own proximity to them eh???
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Phones can't talk directly to each other. The system couldn't handle that. It (and the two phones) would have to recognise when they were close enough for direct contact and decide whether or not to use the network. If you are close enough to the other person, you could always shout or write messages on paper.
As for the delay; for the majority of your 26 seconds, the message is sitting on server equipment, waiting for a suitable time to be slotted in between signals which need to be 'more instant' - like phone conversations.
Texts are cheap because they 1. contain very little information (nothing personal in that remark) and 2. they are low priority.
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Nothing personal taken.
Ok so basically they go into the system and when an available slot is there they are sent off from there very quickly are received it is therefore only the servers equipment is what causes delays in receiving the text message! Right?
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Texts are cheap because they 1. contain very little information (nothing personal in that remark) and 2. they are low priority.
And, 3. there is no guarantee of delivery - so if the server does get inundated, it is perfectly at liberty to throw away texts, and not be in violation of any contractual obligations.
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Really, Wow I have sent kinda emergency texts before and did not know they could do that.
Have even experienced delays as much as 1 day before a text I sent arrived to its destination the next day! I thought lines were down or something!
Wow, I did not know that,.. So they are not regulated by the same regulations as the phone itself and regular calls?
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Really, Wow I have sent kinda emergency texts before and did not know they could do that.
Have even experienced delays as much as 1 day before a text I sent arrived to its destination the next day! I thought lines were down or something!
Wow, I did not know that,.. So they are not regulated by the same regulations as the phone itself and regular calls?
There are no regulations on the delivery of text (but then, there is no regulation that requires a voice call must be able to be put through - even with voice calls, if the network is too busy, the call may not be put through - just you know about it pretty quickly).
I rather suspect there is a financial incentive to making sure the text is delivered, even if 24 hours later, as I rather doubt they could charge a customer for an undelivered text message.
Unfortunately, increasingly, there are people who do rely on delivery of SMS messages (often service engineers are alerted to systems failures in the middle of the night by automatically sent SMS messages, and non-delivery of the message would mean the engineer does not get to fix the system).
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assuming the one day delay is due to the time the data has spent travelling down the cables is must have travelled 1.2 billion miles.
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When the TAT1 cable was first opened to the USA it carried 30 4KHz speech channels, later to make more money the bandwidth was reduced to 3KHz, then an even more cunning scheme was instituted whereby speech control was introduced so that you only got a circuit if you were actually speaking.
I think this was rather a swindle, you only got your monies worth if you sent facsimile pictures.
40 years ago when most telephone circuits to the states went by satellite it was a disaster if you were trying to send pictures, those in the know could add an extra two digits to the dial up code to make sure they got a cable (I have now forgoten them )
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Wow that is interesting. It all Sounds a bit sinister!
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When the TAT1 cable was first opened to the USA it carried 30 4KHz speech channels, later to make more money the bandwidth was reduced to 3KHz, then an even more cunning scheme was instituted whereby speech control was introduced so that you only got a circuit if you were actually speaking.
I think this was rather a swindle, you only got your monies worth if you sent facsimile pictures.
40 years ago when most telephone circuits to the states went by satellite it was a disaster if you were trying to send pictures, those in the know could add an extra two digits to the dial up code to make sure they got a cable (I have now forgoten them )
Hey - the modern GSM system only transmits when you're actually speaking too.
It's called Voice Activity Detection, and it saves battery power (and data volumes).
If you listen to a radio or piece of audio equipment which suffers GSM interference during a nearby phone call, you'll hear that when the person isn't speaking it goes "brrrp...br.....br.....br....brrrrp...br....br...br.....brrrrp", but when they're speaking it just goes "brrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrp". [;D]
You need to listen to the interference on headphones though, otherwise if the phone microphone "hears" the radio then it transmits all the time anyway.
Wow that is interesting. It all Sounds a bit sinister!
Now if you were receiving a call from a mobile and it went completely silent when the person stopped talking - no hiss, no background noise, you'd find it disconcerting (and might even think the call had been dropped). So the phone systems generate what's known as comfort noise which it creates to match the real background when the person is not speaking and the phone is sending very little data. Now that is spooky! [;)]
http://en.wikipedia.org/wiki/Comfort_noise