From the files of the TETON SHORT LINE-  adapted for web use

              A FRESH APPROACH TO BLOCK REQUESTS   3/1/86

       Each block with its associated switchs and adjacent blocks is
       examined from the "center".  The two permitted switchs may be on
       either or both ends and be trailing or facing point. A two bit
       class identifier will be assigned each switch and stored as bits
       5 & 6 of the ADJACENT BLOCK DATA.  The former "West Switch" and
       "East Switch" will be referred to as Switch #1 & Switch #2. They
       will be associated with BRANCH xx04 and xx05 respectively. The
       WEST MAIN & EAST MAIN remain as xxx2 and xx03.  Switch #1 and
       BRANCH xx04 will always be West of Switch #2 and BRANCH xx05 if
       they both exist


       EXAMPLES:

       04 ----\ class 10            E==>>            class 11/------ 05
             #1\     a switch at each end of the block      / #2
       02 ------\------------------------------------------/-------- 03
                                                          sw#2

       04 -----\class 10                              class 11/----- 05
             #1 \ both at West end       both at East end    / #2
       02 -------\--/---------              -------------\--/------- 03
                #2 /                                      \ #1
       05 --------/class 10                        class 11\---------04

        class 00/------ 04                            class 11/------05
             #1/   only one switch       both at East end    / #2
       02 ----/----------------            ---------------/-/--------03
                                                       #1/
       the first bit: 0=trailing point             04---/   class 01
                      1=facing point
          (as viewed from center of the block)

       the second bit: 0=West End of the block
                       1=East  "   "  "    "

       The two bits describing the switch "class" will be stored at
       locations xxx4 and xxx5 in the software. Bit #7 changes with the
       switch position, (reverse=1).   Bit #7 is also used in the BLOCKSPEC
       listing so that three bits fully describe the essential switch
       parameters.  The "1" indicates the BRANCH setting for facing points
       or the OPEN position for trailing.

       examples:  010 = Normal,  Facing, West-end
                  110 = Reverse, Facing, West-end
                  000 = Normal,  Trailing, West-end


        file: newblock.doc  page 1 of 2






                                     RQWEST
                                  +------------+
     get this from                |    IS      |
     xx00 SWITCH DATA     +-------+   THERE A  |
                          |   no  |  SWITCH #2 |
                          |       +------------+
                          |             |   yes
                          |       +------------+
     get this from        |       |   IS IT    |
     xx05 SWITCH DATA     |       |   AT THE   |
                          +-------+ WEST END ? |
                          |   no  |CLASS 00+10 |
                          |       +------------+
                          |             |  yes
                          |       +------------+
     also from xx05       |       |   IS IT    |
                          |       | ALIGNED TO +--------------------|
                          |       | THE BRANCH |   yes         +----------+
                          |       +------------+               |  IS IT   |
                          +-------------|  no     NO ACTION----+ FACING ? |
                                        |                   no | CLASS=10 |
                                  +------------+               +----------+
                                  |    IS      |                    |
                          +-------+  THERE A   |                    |  yes
                          |    no |  SWITCH #1 |               +----------+
                          |       +------------+               |   GET    |
                          |             |                      |  BRANCH  |
                          |             |  yes                 |    05    |
                          |       +------------+               +----------+
                          |       |   IS IT    |
                          |       |   AT THE   |
                          +-------| WEST END?  |
                          |       |CLASS=00+10 |
                          |       +------------+
                          |             |
                          |       +------------+
                          |       |   IS IT    |
                          |       | ALIGNED TO +--------------------|
                          |       | THE BRANCH |   yes         +----------+
                          |       +------------+               |   IS IT  |
                          +-------------| no      NO ACTION----+ FACING ? |
                                  +------------+             no|  CLASS=10|
                                  |    GET     |               +----------+
                                  |  WEST MAIN |                    |  yes
                                  |    02      |               +----------+
                                  +------------+               |   GET    |
                                                               |  BRANCH  |
                                                               |    04    |
file: newblock.doc page 2 of 2                                 +----------+