  In 1959, his teacher George Hughes then employed Sylvan to build a small electro-mechanical computer capable of determining whether input formulae were logical truths, logical falsehoods, or neither—with green, red and amber lights displaying the respective outcomes. He worked out how to build it from scratch using relays and uniselectors discarded by the post office and it was a success, but when run some years later it drew so much power that it blacked out the building it was housed in, ruining several experiments in biology running in the building at the time. The Biology Department insisted that it never be used again (Hyde 2014, 43).