Ripple blanking Input-

It is also connected to logic 1 for normal decoding operation. If it is connected to 0 the display output will be display data for normal 7 segment decoding. All BCD input expect ‘0’ and when BCD input is ‘0’ then 7 segment become off. So that for ‘0’ output it is always connected to logic ‘1’.

Lamp Test-

This is used to check the segment of LED. For normal operation it is connected to logic 1. If it is connected to logic 0 then all LED’s segments of the display will be on.