Eight LED`s are used to indicate the pad currently selected. These LED`s are connected to a decade counter, which sequences the LED`s when it receives a clock pulse.Only one LED can be lit at a time from the decade counter, so although this circuit contains many LED`s only a small drain us placed on the battery. The clock pulse for the decade counter is generated by a 555 timer.
The circuit diagarm for the pad unit is very simple. Six input lines receive the signals from the main controller. I don`t think I need to explain this part of the circuit in detail, although I will mention a few things. Firstly make sure that the re