The computer controlled telescope can accept autoguider input via two methods:

1. LX200 protocol: scope.exe knows about the guiding commands available in the LX200 communications protocol.  Simply hook up the serial port from the guiding computer via a null modem cable to the serial port being used as the LX200 communications port on the computer running scope.exe.  Martin Niemi's superb quickcam autoguider will do this very inexpensively - see 

2. Relay box: The autoguider needs to supply a relay for each direction, or, a +5 VDC TTL signal for each direction, or, a serial connection sending LX200 protocol commands.

If using a relay box, wire the interface circuit such that when a relay closes,  a +5VDC TTL signal is supplied as follows:
If using a control signal, tie the control signals so that the control signal going to logical high raises the input voltage to a +5VDC level as follows:

(this scheme mirrors the four direction buttons on the hand paddle)
  up or north: to pin 13 of the parallel port, down or south: to pin 12 of the parallel port, left or counterclockwise: to pin 10 of the parallel port, right or clockwise: to pins 13 and 12 of the parallel port.

Here is how Juan Herrero hooked up his SBIG ST4 autoguider to the hand paddle:

Purchase a 2 female to 1 male phone wire adapter. Plug the male side to the control board.. Plug the hand paddle to one of the females. The other female will be for the ST-4. Purchase a phone wire with a male plug at one end to plug into the 2 to 1
adapter at the control board. At the other end of the wire. Install the correct computer plug to connect to the ST-4. You need to install 2 small signal diodes in two of the wires. Install the 2 diodes inside the computer plug.
The wire assignment is as follows:

ST-4 action   HAND PADDLE    PARALLEL PORT   ST-4 pins
+5v       white              n/a    ----------------------- 11, 5, 14, 8
-Az       yellow             10     ----------------------- 10
+Az       green              12     ---------|<|----------- 4 *
+Az       black              13     ---------|<|----------- 4 *
-Alt       green              12     ----------------------- 7
+Alt      black              13     ----------------------- 13

* -----|<|----- This symbol represents a diode and they are a must for thing to work.

Both the hand paddle and the ST-4 can be operated at the same time although conflicting simultaneous signals can be sent to the PC in this fashion, resulting in unpredictable actions.

To operate: