What would be the fastest dial-up access speed if phone systemshad 144 dB of dynamic range?
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From: Tim Wescott on 17 Nov 2009 00:37 On Mon, 16 Nov 2009 19:35:57 -0600, Green Xenon wrote: >>"Green Xenon" <green_xenon1(a)yahoo.com> writes: >> >>> Hi: >>> >>> The following is not a homework question. It is a question of my >>> curiosity. >>> >>> Currently dial up internet access has a maximum theoretical speed of > 64 >>> kbps. This is due in part to the 48 dB dynamic range of telephone > systems. >>> >>> If telephones systems are updated so that they have a dynamic range of > 144 >>> dB instead of 48 dB, what will be the maximum theoretical speed of > dial-up >>> internet access? >> >>The easy answer is provided by the capacity formula >> >> C = W * log_2(1+P/N) >> = 4000 * 144/log_10(2) >> = 1.2 Mb/s > > What do "P" and "N" stand for? What does "read up on it" stand for? Search for "Capacity Theorem" and READ. -- www.wescottdesign.com
From: Eric Jacobsen on 17 Nov 2009 16:35 On 11/17/2009 1:55 PM, Green Xenon wrote: >> Green Xenon wrote: >>>> Not that you'd actually see 24 bits even if you increased the quality > of >>>> the D/A converter -- 24 bits of precision is well below the threshold > of >>>> seeing 2nd order effects, and into the really weird stuff. >>> >>> But isn't it possible to build phone systems than can handle 144 dB > [24 >>> bits] of dynamic range? >> Yes. It is also possible to build phone systems with a 20KHz bandwidth. >> Who would pay for it? > > How much does it cost to boost the phone systems from a dynamic range of > 48 dB all the way up to 144 dB? How much have you got to spend? It'll be more than that. -- Eric Jacobsen Minister of Algorithms Abineau Communications http://www.abineau.com
From: Jerry Avins on 17 Nov 2009 17:35 Green Xenon wrote: >> Green Xenon wrote: >>>> Not that you'd actually see 24 bits even if you increased the quality > of >>>> the D/A converter -- 24 bits of precision is well below the threshold > of >>>> seeing 2nd order effects, and into the really weird stuff. >>> >>> But isn't it possible to build phone systems than can handle 144 dB > [24 >>> bits] of dynamic range? >> Yes. It is also possible to build phone systems with a 20KHz bandwidth. >> Who would pay for it? > > How much does it cost to boost the phone systems from a dynamic range of > 48 dB all the way up to 144 dB? More than you want to pay. For myself, I wouldn't pay anything to improve the more than adequate. I have a rich friend who suffered a power failure in a storm and now agitates to have all overhead wired buried. He would be happy to pay triple his current rate in order to make that happen, and thinks that the rest of us should also welcome the change. You seem to agree. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
From: Richard Dobson on 17 Nov 2009 18:29 Green Xenon wrote: .. > Also, could the analog telephone systems be simulated digitally so that > one can experience the nostalgia of dial-up [dialing the phone numbers and > hearing the modem tones] while using cable/DSL so that the speed is much > faster. > Sample it. The modem dialup sound is probably in a sample or effects library somewhere. You could use it as the ring tone on your mobile. You could record the sound of a fax connection. Can't be that different, really. For myself, I feel no nostalgia, didn't think dialup was worth what one had to pay for it, and definitely not the number of times the ISP went down altogether. Punched ticker tape readers - now that was something to get nostalgic about. A prof I know still has a stack of computer punched cards on a shelf, in "as-new" condition. Doubt if he is nostalgic about the week-long turnaround for the results though. Richard Dobson
From: Les Cargill on 17 Nov 2009 23:18
Jerry Avins wrote: > Green Xenon wrote: >>> Green Xenon wrote: >>>>> Not that you'd actually see 24 bits even if you increased the quality >> of >>>>> the D/A converter -- 24 bits of precision is well below the threshold >> of >>>>> seeing 2nd order effects, and into the really weird stuff. >>>> >>>> But isn't it possible to build phone systems than can handle 144 dB >> [24 >>>> bits] of dynamic range? >>> Yes. It is also possible to build phone systems with a 20KHz >>> bandwidth. Who would pay for it? >> >> How much does it cost to boost the phone systems from a dynamic range of >> 48 dB all the way up to 144 dB? > > More than you want to pay. For myself, I wouldn't pay anything to > improve the more than adequate. > > I have a rich friend who suffered a power failure in a storm and now > agitates to have all overhead wired buried. He would be happy to pay > triple his current rate in order to make that happen, and thinks that > the rest of us should also welcome the change. You seem to agree. > > Jerry Does he know about generators? He doesn't need you guys for that. And Florida Flicker and Flash provides power outages whether your power lines are buried or not. -- Les Cargill |