electronic toss-up

EE 94 July/August 1986 74 The electronic version of the well- known coin to toss up prior to com- mencing a footbal match-or any other sports event where this a gen- erally established formality on part of the referee-consists of a row of seven LEDs, the centre one being green, the others red. After having reset the circuit, the odds are exactly equal for either one red LED located next to the green one to light when the toss-up key is pressed; we have, therefore, a left/right decision circuit operating on the basis of pure ar- bitrariness. As to the operation of the circuit, but- ton Si may be pressed at any time to preset counter IC,, which responds with outputting the binary code for 0 at its Qe, Ql and Q2 outputs, causing BCD-to-decimal decoder IC2 to light the corresponding LED, i.e. the green one-D4-at the centre of the row. The preset code for the initial state of the circuit is determined with preset inputs Pm... P3 being tied to ground, causing IC, to load 0000 as...