Hello, please find attached a copy of my circuit. It consists of four 555 timers. Two in monostable mode and two in astable mode. Its function is to operate the two LEDs separately. On pressing SW1, IC3 (monostable) is triggered and outputs a pulse that lasts about 5 sec. This pulse is fed to IC1 (astable) which produces square waves that allows the LED D1 to flash. Similarly on pressing SW2, the same procedure occurs with IC4 and IC2, hence causing LED D2 to flash. The circuit looks fine and Works fine. But what I want to do is the following: When SW1 is pressed, D1 should flash. But if D2 was flashing when I pressed SW1, it should automatically stop. Similarly, when SW2 is pressed, D2 should flash. But if D1 was flashing when I pressed SW1, it should automatically stop. So, can anyone suggest a way of doing this??? Thanks in advance!!!