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This is a 3rd generation circuit that I designed to facilitate the managing of 20 unique events, both input and output. The parallel port on a computer has a total of 5 inputs and 12 outputs. Through the use of latches and buffers, this design allows the parallel port to inexpensively manage a greater number of events.

1) The parallel port interface has a total of 20 contacts on the outside for inputs triggers, such as Infrared Lightbeams, and another 20 contacts for outputs to devices like Relay Switched Outlets.

2) The interface also has contacts for 5V power, such that I can distribute the necessary power to the remote circuits (triggers and relays).

3) The Event Control Software that I wrote monitors the input trigger state and appropriately sets the output state for each of the 20 lines.