Indoor positioning System-The most reliable positioning System in the world to find the position of an object in an Indoor environment where Global Positioning System does not work.INDOOR POSITIONING SYSTEM is a system in ?which we can locate the position of an object in an ?indoor environment utilizing ultrasonic waves ?generated by narrow directional ultrasonic ?transmitter. To achieve the objective of position ?detection, we have designed ultrasonic transmitter ?and receiver circuits, RF transmitter, and receiver ?for synchronization purposes. By implementing ?time of arrival method, we have located the ?position of an object. It is accomplished by using ?distances between the multiple receivers and a ?single transmitter located in a room. RF signal ?starts the timer and when ultrasonic waves will ?reach at the receiver end, it will stop the timer and ?then the extracted signal from the receiver is ?transmitted to the microcontroller for locating ?position of an object. The systems using ultrasonic ?waves have the advantage that it can be built on ?low cost and has relatively high accuracy to detect ?the position of an object in an indoor environment.?