Steve Underwood wrote:> Tim Wescott wrote: > >> Steve Underwood wrote: >> >>> Tim Wescott wrote: >>> >>>> Steve Underwood wrote: >>>> >>>>> Don Bowey wrote: >>>>> >>>>>> On 4/25/06 12:14 AM, in article e2ki8j$cuh$1@home.itg.ti.com, "Steve >>>>>> Underwood" <steveu@dis.org> wrote: >>>>>> >>>>>> >>>>>>> Joerg wrote: >>>>>>> >>>>>>>> Hello Jim, >>>>>>>> >>>>>>>> >>>>>>>>> 1200 baud FSK changes frequency in a _single_ cycle, so >>>>>>>>> period-type >>>>>>>>> demodulation goes to crap quickly in the presence of noise. >>>>>>>>> >>>>>>>> >>>>>>>> Zero-crossers are pretty much a thing of the past here, just >>>>>>>> like they >>>>>>>> are for medical ultrasound Doppler. You can do it in the digital >>>>>>>> domain >>>>>>>> these days. All it takes is a good uC such as the MSP430. But not a >>>>>>>> version with a puny 10 or 12 bit converter. They offer some that >>>>>>>> convert >>>>>>>> to 16 bits. >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> What's wrong with a 12 bit converter? The entire telephone >>>>>>> network uses >>>>>>> 12 bits. >>>>>>> >>>>>>> Steve >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> No, the telco network is 8 bits, 8000 times each second. >>>>> >>>>> >>>>> >>>>> >>>>> No, the telco network is 12 bits, compressed to 8 bits in a pseudo >>>>> logarithmic manner. Its dynamic range is 12 bits. >>>>> >>>>> Steve >>>> >>>> >>>> >>>> No, it's dynamic range is 48dB -- but only in the sense that you can >>>> listen to something, then the same thing 48dB down. You _can't_ >>>> listen to one signal at max amplitude at the same time you're >>>> hearing another one, undistorted, 48dB down. >>>> >>>> This is fun. I'm waiting for the response to this post that starts >>>> out "No, ..." >>>> >>> No. The SDR of u-law and a-law is a lot less than 48dB. It is more >>> like 30dB. 48dB would be the range of an 8 bit number. The telephone >>> network kinda has 5 bit numbers and 3 bit exponents. >>> >>> Steve >> >> >> Oh. Dangit. How'd I get 12 * 6 = 48? Must be the New Math. >> > > "Forty-eight? How did forty-eight get into it?" I hear you cry. > Well, forty-eight is 6*8, don't you see? > (Well, you ask a silly question, and you get a silly answer.) > > Apologies to Tom Lehrer :-) > > SteveWell, I think that's where it came from, too -- but it was supposed to be 12 * 6. My kid does that. I try to impress upon him the importance of showing your work for just that reason. Still, he (and I) persist in doing things in our heads with little errors. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Posting from Google? See http://cfaj.freeshell.org/google/
ping: Jim Thompson
Started by ●April 24, 2006
Reply by ●April 26, 20062006-04-26
Reply by ●April 26, 20062006-04-26
"Tim Wescott" <tim@seemywebsite.com> wrote in message news:JcWdnZO1XNhnF9LZRVn-vw@web-ster.com...> > Well, I think that's where it came from, too -- but it was supposed to be > 12 * 6. My kid does that. I try to impress upon him the importance of > showing your work for just that reason. Still, he (and I) persist in > doing things in our heads with little errors. > > -- > > Tim Wescott > Wescott Design Services > http://www.wescottdesign.comWell what is really fun to show is how to improperly reduce a fraction and still get the right result 16 1 --- = --- 64 4 just cancel out the sixes. Try it with 19 --- 95 cancel the nines and you get 1/5 Of course the trick is there are four cases where this works when 2 digits are divided by two digits. Clay
Reply by ●April 26, 20062006-04-26
On 4/25/06 8:38 PM, in article _vCdneqlIOqxdtPZRVn-hg@rcn.net, "Jerry Avins" <jya@ieee.org> wrote:> Don Bowey wrote: >> On 4/25/06 9:49 AM, in article erudncGPy7ioztPZRVn-gQ@rcn.net, "Jerry Avins" >> <jya@ieee.org> wrote: >> >> >>> Don Bowey wrote: >>> >>>> On 4/25/06 12:14 AM, in article e2ki8j$cuh$1@home.itg.ti.com, "Steve >>>> Underwood" <steveu@dis.org> wrote: >>>> >>>> >>>> >>>>> Joerg wrote: >>>>> >>>>> >>>>>> Hello Jim, >>>>>> >>>>>> >>>>>> >>>>>>> 1200 baud FSK changes frequency in a _single_ cycle, so period-type >>>>>>> demodulation goes to crap quickly in the presence of noise. >>>>>>> >>>>>> >>>>>> Zero-crossers are pretty much a thing of the past here, just like they >>>>>> are for medical ultrasound Doppler. You can do it in the digital domain >>>>>> these days. All it takes is a good uC such as the MSP430. But not a >>>>>> version with a puny 10 or 12 bit converter. They offer some that convert >>>>>> to 16 bits. >>>>> >>>>> What's wrong with a 12 bit converter? The entire telephone network uses >>>>> 12 bits. >>>>> >>>>> Steve >>>> >>>> >>>> No, the telco network is 8 bits, 8000 times each second. >>> >>> The eight bits are derived via A-law or mu-law from 12-bit data. >>> >>> Jerry >> >> >> Only if the bits are being used to provide a voice channel, as contrasted to >> a 64 kbit/s digital channel or concatinated digital channels. > > When you send bits, you send bits. The converter used for sending voice > has 12 bits. (It will have 8 outputs if the pseudo-log converter is > integrated with it.) > > JerryAt the per channel level, the only place where more than 8 bits are used is in the exchange between the codec and channel units, where 14 bits are used to set the PAM polarity, Cord, and level within the cord, switches for the codec. Don
Reply by ●April 27, 20062006-04-27
Don Bowey wrote:> On 4/25/06 8:38 PM, in article _vCdneqlIOqxdtPZRVn-hg@rcn.net, "Jerry Avins" > <jya@ieee.org> wrote: > > >>Don Bowey wrote: >> >>>On 4/25/06 9:49 AM, in article erudncGPy7ioztPZRVn-gQ@rcn.net, "Jerry Avins" >>><jya@ieee.org> wrote: >>> >>> >>> >>>>Don Bowey wrote: >>>> >>>> >>>>>On 4/25/06 12:14 AM, in article e2ki8j$cuh$1@home.itg.ti.com, "Steve >>>>>Underwood" <steveu@dis.org> wrote: >>>>> >>>>> >>>>> >>>>> >>>>>>Joerg wrote: >>>>>> >>>>>> >>>>>> >>>>>>>Hello Jim, >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>>>1200 baud FSK changes frequency in a _single_ cycle, so period-type >>>>>>>>demodulation goes to crap quickly in the presence of noise. >>>>>>>> >>>>>>> >>>>>>>Zero-crossers are pretty much a thing of the past here, just like they >>>>>>>are for medical ultrasound Doppler. You can do it in the digital domain >>>>>>>these days. All it takes is a good uC such as the MSP430. But not a >>>>>>>version with a puny 10 or 12 bit converter. They offer some that convert >>>>>>>to 16 bits. >>>>>> >>>>>>What's wrong with a 12 bit converter? The entire telephone network uses >>>>>>12 bits. >>>>>> >>>>>>Steve >>>>> >>>>> >>>>>No, the telco network is 8 bits, 8000 times each second. >>>> >>>>The eight bits are derived via A-law or mu-law from 12-bit data. >>>> >>>>Jerry >>> >>> >>>Only if the bits are being used to provide a voice channel, as contrasted to >>>a 64 kbit/s digital channel or concatinated digital channels. >> >>When you send bits, you send bits. The converter used for sending voice >>has 12 bits. (It will have 8 outputs if the pseudo-log converter is >>integrated with it.) >> >>Jerry > > > > At the per channel level, the only place where more than 8 bits are used is > in the exchange between the codec and channel units, where 14 bits are used > to set the PAM polarity, Cord, and level within the cord, switches for the > codec. > > DonYour words have an intriguing surreal quality. :-) Steve
Reply by ●April 27, 20062006-04-27
On 4/27/06 7:38 AM, in article e2ql0j$6v3$1@nnews.pacific.net.hk, "Steve Underwood" <steveu@dis.org> wrote:> Don Bowey wrote: >> On 4/25/06 8:38 PM, in article _vCdneqlIOqxdtPZRVn-hg@rcn.net, "Jerry Avins" >> <jya@ieee.org> wrote: >> >> >>> Don Bowey wrote: >>> >>>> On 4/25/06 9:49 AM, in article erudncGPy7ioztPZRVn-gQ@rcn.net, "Jerry >>>> Avins" >>>> <jya@ieee.org> wrote: >>>> >>>> >>>> >>>>> Don Bowey wrote: >>>>> >>>>> >>>>>> On 4/25/06 12:14 AM, in article e2ki8j$cuh$1@home.itg.ti.com, "Steve >>>>>> Underwood" <steveu@dis.org> wrote: >>>>>> >>>>>> >>>>>> >>>>>> >>>>>>> Joerg wrote: >>>>>>> >>>>>>> >>>>>>> >>>>>>>> Hello Jim, >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>>> 1200 baud FSK changes frequency in a _single_ cycle, so period-type >>>>>>>>> demodulation goes to crap quickly in the presence of noise. >>>>>>>>> >>>>>>>> >>>>>>>> Zero-crossers are pretty much a thing of the past here, just like they >>>>>>>> are for medical ultrasound Doppler. You can do it in the digital domain >>>>>>>> these days. All it takes is a good uC such as the MSP430. But not a >>>>>>>> version with a puny 10 or 12 bit converter. They offer some that >>>>>>>> convert >>>>>>>> to 16 bits. >>>>>>> >>>>>>> What's wrong with a 12 bit converter? The entire telephone network uses >>>>>>> 12 bits. >>>>>>> >>>>>>> Steve >>>>>> >>>>>> >>>>>> No, the telco network is 8 bits, 8000 times each second. >>>>> >>>>> The eight bits are derived via A-law or mu-law from 12-bit data. >>>>> >>>>> Jerry >>>> >>>> >>>> Only if the bits are being used to provide a voice channel, as contrasted >>>> to >>>> a 64 kbit/s digital channel or concatinated digital channels. >>> >>> When you send bits, you send bits. The converter used for sending voice >>> has 12 bits. (It will have 8 outputs if the pseudo-log converter is >>> integrated with it.) >>> >>> Jerry >> >> >> >> At the per channel level, the only place where more than 8 bits are used is >> in the exchange between the codec and channel units, where 14 bits are used >> to set the PAM polarity, Cord, and level within the cord, switches for the >> codec. >> >> Don > > Your words have an intriguing surreal quality. :-) > > SteveAnd yours appear to be mindless.
Reply by ●April 30, 20062006-04-30
Don Bowey wrote:> On 4/25/06 9:49 AM, in article erudncGPy7ioztPZRVn-gQ@rcn.net, "JerryAvins"> <jya@ieee.org> wrote: > >> Don Bowey wrote: >>> On 4/25/06 12:14 AM, in article e2ki8j$cuh$1@home.itg.ti.com, "Steve >>> Underwood" <steveu@dis.org> wrote: >>> >>> >>>> Joerg wrote: >>>> >>>>> Hello Jim, >>>>> >>>>> >>>>>> 1200 baud FSK changes frequency in a _single_ cycle, so period-type >>>>>> demodulation goes to crap quickly in the presence of noise. >>>>>> >>>>> >>>>> Zero-crossers are pretty much a thing of the past here, just like they >>>>> are for medical ultrasound Doppler. You can do it in the digitaldomain>>>>> these days. All it takes is a good uC such as the MSP430. But not a >>>>> version with a puny 10 or 12 bit converter. They offer some thatconvert>>>>> to 16 bits. >>>> >>>> What's wrong with a 12 bit converter? The entire telephone network uses >>>> 12 bits. >>>> >>>> Steve >>> >>> >>> No, the telco network is 8 bits, 8000 times each second. >> >> The eight bits are derived via A-law or mu-law from 12-bit data. >> >> Jerry > > Only if the bits are being used to provide a voice channel, as contrastedto> a 64 kbit/s digital channel or concatinated digital channels. > > DonOK alligator breath, explain v.90 modems. -- JosephKK Gegen dummheit kampfen die Gotter Selbst, vergebens. --Schiller
