emjej@uokvax.UUCP (10/28/83)
#R:ihuxq:-35000:uokvax:2700004:000:1078 uokvax!emjej Oct 25 11:11:00 1983 By Nyquist, to accurately digitize a signal containing frequencies bounded above by Fmax Hz, one has to take at least 2 * Fmax samples per second. Voice bandwidth is canonically 3KHz, but they use 4KHz (I guess for slack or nicer factors of 4 than 3). If each sample is one byte, then they are sending each second 8000 samples * 8 bits/sample = 64,000 bits/second for a voice channel. This is rather more than 300 bits/second, or even 9600 bits/second. Now, if the Bell System (or union of the pieces after January 1st) can just trash all that antiquated equipment...but of course, they can't, not very quickly; especially not the local operating companies, who are at the bottom of the pyramid and hence have the most equipment that needs to be junked. The long distance services have the advantage in that respect, although even T1 "digital" trunks can only be used for data if they're dedicated, since the designers, thinking that no one would send data over them, steal the least significant bit of every nth sample to send on/offhook info and the like. James Jones