constellation offers higher encoding density with its "quintbits" (2^5=32),   
   as opposed to the 16-point constellation with its "quadbit" structure   
   (2^4=16).   
      
   With a given fixed symbol rate (e.g., 2400), the 16-point constellation can   
   deliver data exchange rates of 9600 bps (2400X4). The more-complicated   
   32-bit constellation offers an intrinsically higher data rate capacity of   
   12,000 bps (2400 symbols/sec X 5).  It's also more susceptible to channel   
   noise because you have to push the individual decision points closer   
   together, and any minor noise perturbation is more likely to cause the   
   distant receiver to make a decoding error.   
      
   However, instead of using the higher density of the 32-point constellation   
   for speed purposes, suppose you use its added complexity for noise immunity   
   purposes to derive a performance boost.  TCM does just that.   
      
   Instead of operating at 12,000 bps, V.32 TCM transmission remains at 9600   
   bps with twice as many constellation points as it needs.  The extra   
   constellation bits produce a redundant bit.  This fifth bit is used as an   
   embedded "checksum" to produce intelligent transmission. Decision rules are   
   used in both the transmitter and the receiver to produce an orderly   
   transmission that is designed to maximize noise immunity.   
      
   The redundant bit serves an error-detection function similar to the ninth   
   bit used for parity in 8-bit PC memory systems.  The memory bit doesn't   
   prevent errors from occurring; however, it flags them and prevents them   
   from propagating.   
      
   With TCM, the fifth bit acts to help the remote receiver make a high-   
   probability choice among possible alternatives when  channel noise has   
   distorted the incoming signal.  It doesn't absolutely guarantee error free   
   communication, but helps reduce the probability of errors. The net result   
   is about 4 decibels (a little more than double) the S/N ratio of a non   
   encoded system.   
      
   TSB38/37A - A network model description and set of testing procedures which   
   are defined in Technical Standard Bulletins of the Telecommunications   
   Industry Association. The TSB37A test suite is used with modem performance   
   test procedures given in TSB38.  It is widely used today for comparisons   
   between modems. It models the network as two independent local loops with a   
   four-wire trunk connection between them.  Impairments primarily found in   
   the digital network are specified in proportion to their believed presence   
   in the network.   For instance, up to three PCM links are included in the   
   tests. ADPCM is also represented.   
      
   There are also minimal tests that represent the older analog equipment in   
   the network. Each loop and trunk connection specified is assigned a   
   Likelihood of Occurrence percentage (LOO).  By multiplying the scores for   
   the loop combination and the trunk, an overall LOO can be assigned to a   
   given test.  A LOO of 4% indicates that the results of that test represent   
   4% of the expected connections in the actual network.   
      
   UART - (U)niversal (A)synchronous (R)eceiver (T)ransmitter - a   
   semiconductor which interfaces serial ports to the processor buss.   
      
       FIFO - (F)irst-(I)n-(F)irst-(O)ut - describes the data handling   
       technique utilized by high-performance buffered UARTs such as the   
       NS16550AFN.   
      
   V.8 - Procedures for starting sessions of data transmission over the   
   general switched telephone network   
      
   V.17 - ITU-T recommendation of Facsimile operation at up to 14400bps.   
      
   V.18 - Operational and inter-working requirements for modems operating in   
   the text telephone mode   
      
   V.21 - ITU-T recommendation for modem communications at 300bps. NOTE: this   
   recommendation is widely utilized outside of the United States and Canada   
   where the Bell 103 protocol is more prevalent.   
      
   V.22 - ITU-T recommendation  for modem communications at 1200bps. NOTE:   
   This recommendation is compatible with the Bell 212A protocol which is   
   prevalent in the US and Canada for devices which operate at 1200bps.   
      
   V.22bis - ITU-T recommendation for modem communications at 2400bps.   
   Includes an automatic link negotiation fall-back to 1200bps and   
   compatibility with Bell 212A/V.22 modems.   
      
   V.25 - ITU-T recommendation which specifies a 2100Hz answer tone which is   
   different from the Bell answer tone used in the US and Canada.   
      
   V.25bis - ITU-T recommended command language for modems.   
      
   V.27ter - ITU-T modulation scheme used in Group 3 Facsimile for image   
   transfer at 2400 and 4800 bps. It is also used for 4-wire leased line   
   modems.   
      
   V.29 - ITU-T modulation scheme used in Group 3 Facsimile for image transfer   
   over dial-up lines at 9600 and 7200 bps.   
      
   V.32 - ITU-T recommendation for modem communications at 9600 and 4800bps.   
   Incorporates fall-back/fall-forward logic for operation on impaired phone   
   lines.   
      
   V.32bis - ITU-T recommendation which extends the V.32 connection range to   
   incorporate link rates of 4800, 7200, 9600, 12000, and 14400bps.   
   Incorporates logic that falls back to the next lower speed when line   
   quality deteriorates, and fall back further as necessary. Also incorporates   
   fall forward and rapid rate negotiation logic.   
      
   V.32terbo - 19200bps, with fall back to 16800bps. Designed by AT&T, and is   
   public domain, so any manufacturer can use this standard and put it into   
   their modems. USR has further extended this to support a proprietary link   
   rate of 21600bps.   
      
   V.32turbo - A modulation protocol developed by Rockwell which extended V.32   
   link rates to 12000bps.   
      
   V.34 - ITU-T recommendation for data signalling rates of up to 33.6kbps for   
   use on the general switched telephone network and on leased point-to-point   
   2-wire telephone-type circuits.   
      
   V.42 - ITU-T recommendation for modem communications that defines a   
      
   --- MPost/2 v2.0a   
    * Origin: Marsh BBS (c) Dawson Creek BC Canada (1:17/23)