Sometimes when we test digital equipment at home we require to know the binary state at any particular point. For that you can use this simple circuit. This circuit uses four LED’s to give you the indication of the logic state. Like if Green LED1 glows means you have provided the 10 as binary state and so on. This simple circuit is based on inverter IC 7404 with four resistor and four LED’s. CD7404 is the most commonly used Complementary Metal Oxide Semiconductor (CMOS) chip. It comes in a 14 pin Dual Inline Package (DIP). It has small notch on one side which identifies as pin 1.It consists of 6 independent NOT gate on a single chip. Each gate has 1 inputs and 1 output. Working voltage range of IC is from 5V to 16V. It can deliver approx.10mA at 12V but this can be reducing as power supply voltage reduces.