This simple polarity cum continuity tester indicates the polarity of many components like diodes, LED including Zener diode and infrared LED. This can also be used to check the above components are good or bad before mounting them on the PCB. Many a times, it happens that people are unable to identify the polarity of the component which leads to wrong soldering of components that damages the components or it may damage the whole circuit. This circuit can also be used as continuity tester, to test the continuity of the circuit. The circuit is made with the help of two transistor configured as astable multivibrator. Outputs of both the transistors are out of phase with each other meaning that if  output of one transistor is high then output of another transistor will be low or vice versa.