Parallel Port 3 Axis CNC Driver, Opto-Isolated, Unipolar Steppers

Step 6 Plug in the ICs, Interconnects

Opto-Coupler's are labeled LTV827

The 16-pin socket., labeled OPTO2, is shared by 2 8-pin opto-couplers.
The dots on the ICs go on the same end as the notch in the sockets.

The other 8-pin opto-coupler goes into the socket labeled OPTO

If you purchased a programmed and tested chip from my Store.
Carefully plug it into the socket, aligning the notch on the socket and the dot on the IC.

Otherwise, program a 16F870 with the HEX file in the .ZIP in step 1.
Check the readme for fuses or the image below.