Seven Push button NO switches from left to right are a) FF Reset b) Key 0 c) Key 1 d) Key 2 e) Key 3. f) Key 4 g) Key 5 Press and hold numeric keys for few seconds to stabilize all ICs to display proper number in unit place. SR Flip Flop has been used for Key Board. D-Flip Flop "Parallel In Parallel Out" mode has been used to shift Unit place number to Ten place and Ten place to Hundred place. Due to out of space only 000 to 555 could be displayed.
To reset first press 0 key then press Reset key.
