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.‎