Universal IR Controller for a PC -- Circuit & Design Ideas (September 1998): A number of readers have pointed out that the circuit as shown won't work, as the open collector outputs of the 7405 can't source current, and can only act as current sinks. To fix the problem, the end of R5 should be disconnected from ground and attached to the outputs of the inverters. The anode of D1 should then be isolated from the inverters, and instead taken to +5V. The other alternative is to simply swap the 7405 with the 7404 hex inverter, which can source the required current.