TELECOM Moderator <telecom@eecs.nwu.edu> (08/03/90)
It's hard to believe that after 40 or 50 years, Dick Tracy is still ahead of the times with his Two-Way Wrist TV. But arm's-length communications seems to be getting a little closer to reality with Motorola's announcement that it had begun national distribution of its combined wristwatch/pager this month. This combination will be sold for about a year by pager dealers, and probably by 1992 will be on sale in retail stores as well. This is a joint venture with Timex, and the product looks much like a typical black LCD watch, however it is bulkier because of the small battery which operates the pager for 45 days, and the extra buttons required to operate the pager. When messages come in, the same screen used by the timepiece will instead display the phone number of the caller on the liquid crystal screen. The unit will beep as loud as normal pagers. It operates on the Golay Sequential Coding and Post Office Standard Advisory Group Code systems, the two primary paging systems used. Motorola says they have targeted this new watch/pager combination at people who have never used a pager before. Motorola is actually second on the market with something like this: earlier this year, a company on the west coast called AT&E started marketing its own wrist pager, with similar features. With the Motorola unit at least, after you buy it, you take it to the radio paging company of your choice and they activate it, like they would any other pager. In most cases, the dealer or store selling the unit will already have an arrangement with some service provider, much as cellular phones are marketed now. The price is going to be in the $150 - $200 range, presumably if a deal is cut with the paging company. Now we can all be Dick Tracy! (Almost, anyway ... still no way to talk back to it, or see pictures on it. That'll be next, I guess.) Patrick Townson
"Craig R. Watkins" <CRW@icf.hrb.com> (08/03/90)
In article <10353@accuvax.nwu.edu>, telecom@eecs.nwu.edu (TELECOM Moderator) writes: > It operates on the Golay Sequential Coding and Post Office Standard > Advisory Group Code systems, the two primary paging systems used. I've been looking for spec of GSC (Golay Sequential Code). Anyone have any pointers? Craig R. Watkins Internet: CRW@ICF.HRB.COM HRB Systems, Inc. Bitnet: CRW%HRB@PSUECL.Bitnet +1 814 238-4311 UUCP: ...!psuvax1!hrbicf!crw
rpw3%rigden.wpd@sgi.com (Rob Warnock) (08/04/90)
In article <10398@accuvax.nwu.edu> CRW@icf.hrb.com (Craig R. Watkins) writes: | I've been looking for spec of GSC (Golay Sequential Code). Anyone | have any pointers? I suspect that what I am about to say will be of no use as far as pointing you at a spec for the GSC as used by pagers, but for those interested in error-correcting codes in general... From Lin & Costello, "Error Control Coding", (P-H 1983) p.134ff: "THE GOLAY CODE "The (23,12) Golay code is the only known multiple-error-correcting binary perfect code which is capable of correcting any combination of three or fewer random errors in a block of 23 digits. This code has abundant and beautiful algebraic structure. Since its discovery by Golay in 1949, it has become a subject of study by many coding theorists and mathematicians.... "The (23,12) Golay code is either generated by g1(X) = 1 + X^2 + X^4 + X^5 + X^6 + X^10 + X^11 or by g1(X) = 1 + X + X^5 + X^6 + X^7 + X^9 + X^11 "Both g1(X) and G2(X) are factors of X^23 + 1 = (1 + X)g1(X)g2(X). The encoding can be accomplished by an 11-stage shift register with feedback connections according to either g1(X) or g2(X). "...There are several practical ways to decode the (23,12) Golay code up to its error-correcting capacity t=3. two of the best are discussed in this section. Both are refined error-trapping schemes." They go on to describe a version of the Kasami decoder and the systematic search decoder, with plusses and minuses for each. Elsewhere in the book they note that the (23,12) Golay code and the (2^N - 1, 2^N - N - 1) Hamming single-error correcting codes are the only known perfect binary error-correcting codes. The only known perfect non-binary error correcting codes are the general- ized Hamming codes and the double-error-correcting (11,6) code over GF(3), also discovered by Golay. [Peterson & Weldon, "Error-Correcting Codes", (MIT 1972), p.143] "There are a number of results indicating that perfect codes are scarce, and it even seems quite likely that there are no others." [Ibid., p.121] For those who wonder how this connects with pagers, note that by doubling (well, 23/12'ths) the number of bits sent and using the above Golay code, you can get nearly error-free reception with bit error rates approaching 10%. (Occasionally more than three errors will occur in a block of 23 bits, then the whole 12-bit data byte is garbled.) Not bad, not bad... Rob Warnock, MS-9U/510 rpw3@sgi.com rpw3@pei.com Silicon Graphics, Inc. (415)335-1673 Protocol Engines, Inc. 2011 N. Shoreline Blvd. Mountain View, CA 94039-7311
Arnold Robbins <arnold%audiofax.com@mathcs.emory.edu> (08/10/90)
In article <10353@accuvax.nwu.edu> telecom@eecs.nwu.edu (TELECOM Moderator) writes: >It's hard to believe that after 40 or 50 years, Dick Tracy is still >ahead of the times with his Two-Way Wrist TV. >Now we can all be Dick Tracy! (Almost, anyway ... still no way to talk >back to it, or see pictures on it. That'll be next, I guess.) Not that the following has much to do with Telecom, but I seem to remember some years ago seeing a wrist-watch television by, I think, Seiko. It had an LCD screen on a wristband, and a separate small box for the actual TV tuner electronics. I think it had an earphone jack, too. It didn't seem all that practical, and had a hefty (~ $400) price tag, but it certainly was an existence proof for TV-on-the-wrist. Arnold Robbins AudioFAX, Inc. 2000 Powers Ferry Road, #220 / Marietta, GA. 30067 INTERNET: arnold@audiofax.com Phone: +1 404 933 7600 UUCP: emory!audfax!arnold Fax: +1 404 933 7606