After reading an H-Bridge design from Chuck McManis in handyboardmail.txt, and follow-up from Jeff Keyser, I decided to build one of my own. Yes, it works. The file HBridge.gif will show the exact circuit I built, along with part numbers, pinouts, etc.. Construction notes.. The circuit comes with NO WARRANTY, so if it doesn't work, or blows up in your face, you are solely responsible for the consequences. I can tell you that it works for me, running 12 volt motors... and I am told it runs 6 volt motors for Jeff. The ratings for TIP 120 and TIP 125 are 5 Amp continuous, 8 Amp surge. this is assuming proper heatsinks on these transistors to keep them from getting too hot. USE HEATSINKS!! BIG ONES! The circuit should DEFINETLY be fused. I am using separate 4.5 Amp polyswitch fuses for each motor.. The Forward and Reverse circuits should NEVER be active at the same time. This would result in LOTS of current through the TIP transistors, and likely some strong odors from where your circuit used to be! If you are driving the optocouplers from the HandyBoard motor outputs, this should not present a problem. The 1K resistor between the optocoupler and base of 2n2907 was added by Jeff, and described as optional. My board required them to keep from burning up the outputs of the 4n33's.. If you are using individual heatsinks for the TIP's, you may wish to put 120/125 pairs A/C, and B/D back to back, doubling the effective heatsink area, since only one of each pair should be active at any given time. This is possible because their tabs are connected to their collecors, which are connected electrically anyway. If I can assist, I can be reached at Many thanks to Chuck McManis and Jeff Keyser for the circuit.. I didn't invent it, I only drew the picture... Lyle Hazelwood