Marco Polo is a self-contained 2-way radio system, like a walkie-talkie. When in Track mode, the handheld Marco Polo locator sends a signal to the “tag” you place on the item to be tracked, once every 5 seconds. Each time the tag on the pet “hears” the signal from the locator, it responds with a return signal. The locator then measures the strength of the signal coming back from the tag and finds the direction it came from. Both pieces of information are then displayed on the locator’s screen. Then, you simply follow the arrow pointing to the tag and note the signal strength getting higher as you get closer. If you are not careful - you will step on the tag!