When the area around the other party is noisy & it is difficult to hear, you can reduce the surrounding noise to make the speaker's voice easier to hear just by pressing the dedicated button. Simply attach the key finder/key detector to items that you often misplace, & use the handset to find them quickly & easily. You can see roughly how close you are to your lost item on the LCD screen, & both the handset & key finder/key detector beep when being searched for, making them easy to find. You can add up to four key finders/key detectors.