The NaTKiT1 Digital I/O Kit provides the hardware needed for NaTKiT1 to accept user input from micro switches. The kit consists of a 24 channel digital I/O board, an external 50 way screw terminal board and a 50 way ribbon cable to connect them. NaTKiT1 reserves 8 of the 24 channels for itself. In the future the remaining 16 channels will be available to the user though the current software issue does not support this.
whip the cover off the PC,
Now connect the terminal board to the I/O board using the ribbon cable. The connectors on the ribbon have a key way to ensure correct insertion. So you can test the installation connect a single pole, normally open switch, between terminals 1 and 2 on the terminal board. You could improvise a switch with two bits of wire.
To test the board you now have to tell NaTKiT1 that the board is there. Run the programme select Engineer then System maintenance. The choice Dig I/O Address (Hex) should be showing Not there. Set the address to the I/O board's default 2C0 and then select the TEST below Dig I/O Address (Hex). Applying a short circuit between pins 1 and 2 should now make the character T appear briefly. A short circuit between pins 3 and 4 should make RETURN appear briefly.
The level between terminals 11 and 12 will be high when the FAIL prompt is visible and low at all other times. If the Operator Fail Check is not active then this fail flag will always be valid. If the Operator Fail Check is active then the fail flag will only be valid when the Test in progress flag is low.
All the even numbered terminals are commoned and at ground.