switches k2 k6 and k0 are connected to input line 688c through respective diodes 811 812 and 813 and driver 814 line 688c is also connected to ground line 624 by resistor 815 switches k3 k7 pr and sw6 are connected to input line 688d through respective diodes 816 817 818 and 819 and driver 820 a resistor 821 connects line 688d to ground line 624 through driver 820 the operation of the control system for my copier can best be understood by reference to fig3 to 32 referring now to fig3 a to 30c the main program of my control system starts at block 830 when power is first supplied to the machine as indicated by block 830 the control circuit prepares for normal operation by initializing the peripheral interface adapters 676 and 678 and the memory 674 the cold start status bit is then set and an internal warm up timer is cleared block 832 a general time out timer which provides a maximum amount of time the program counter should not exceed is also cleared block 834 at this point line 688g is grounded and line 696f is raised to logic one to illuminate the 34 please wait 34 led 760f block 836 the print flag print possible and print in progress status bits are cleared blocks.