Install the following parts:

R5, R6, R7 - 220R resistors
R17 - 390K resistor
R18, R19, R20 - 8M2 resistors
R177, R182, R250, R251, R252 - 270K resistors
R246 - 220K resistor
R262, R263, R264, R265 - 1K0 resistors
R266, R267, R268, R269 - 2K2 resistors

C9, C10, C11, C12 - 1n0 capacitors
C30, C44, C58, C78 - 0.1uF capacitors

D42, D43, D44 - each 3 x 1N4148 diodes in series
(mount two sticking vertically out of the board and
one across the top)

D54, D64, D65, D66, D67, D68 - 1N4148 diodes
D57 - BAT85 schottky diode

IC6 - 74LS14 hex inverter
IC7 - 4N28 optoisolator
IC16 - LM324 quad opamp

P11, P12 - 8 pin DIN sockets, pcb mounting

L1 - wire link in 0v position
L2 - wire link in +5v position

There is also a 470R resistor suggested between
pins 4 and 14 on IC6.  There was a space on the
circuit board for mine, but on some versions you 
may have to solder the resistor on top of the chip.