Original Hardware Schematics
Maximize window and select 50 X 80 for better viewing!
This is the schematics as published by the author Henk Schaer (used to be file schema.txt). 

                                                  +5V
 15..30V                                           |14
                  +-------+                     +--+--+
V+ ]--|>|---+-----+ 78L05 +--- +5V              | 7407|
            |     +---+---+                     +--+--+
            |         |                            |7
            |        GND                          GND
            |     +-------+               A   K
            +-----+ 78L12 +--- +12V ------[LED]------[1k]----GND
                  +---+---+              "Power"
V- ]--- GND           |
                     GND                  A   K
                                Vpp ------[LED]------[1k]----GND
                                       "Activity"
                                                      Vdd
                                                       |14
                          Vdd-[10K]--+       +---------+--------+
                  1|\  2             |     13|                  |
  D0 (2)-----------+  >--------------+-------+ RB7/Data         |
                   |/                |       |                  |
      +5V-[10k]-+                    |       |                  |
                | 12 /|13            |       |    PIC 16C84     |
Busy (11)-------+--<  +--------------+       |     18 pin       |
                     \|                      |    ZIF Socket    |
                           Vdd-[10k]--+      |                  |
                  3|\  4              |    12|                  |
   D1 (3)----------+  >---------------+------+ RB6/Clock        |
                   |/                        |                  |
                           Vpp-[10K]--+      |                  |
                  5|\  6              |     4|                  |
   D2 (4)----------+  >---------------+------+ -MCLR/Vpp        |
                   |/                        |                  |
                                             +---------+--------+
                                                       |5
                                             +5V       GND
                                             |
                                  +--[10K]---+
                                  |          |
                 11|\  10         |      B |/ E
             +-----+  >----[10K]--+--------|     PNP
             |     |/                      |\ C
             |                               |
             |                               +---Vdd
             |                               |
             |                             [10K]
             |                               |
             |                              GND
             |
             |                              +12V
             |                               |
             |                    +--[10K]---+
             |                    |          |
             |    9|\  8          |      B |/ E
   D3 (5)----+-----+  >----[10K]--+--------|     PNP
                   |/                      |\ C
                                             |
                                             +---Vpp
  GND (19)------GND                          |
                                           [10K]
                                             |
                                            GND


--------------------------------------------------------------------------------