48 Forerunner ® 301 Owner’s ManualAPPENDIX > H EART RATE MONITOR INFORMATIONHeart Rate Monitor InformationWhat is pairing and how does it work?Pairing occurs automatically when you turn on theForerunner and you are wearing the heart rate monitor.Pairing allows the Forerunner to receive reliable heart ratedata from your heart rate monitor by means of a secure,digital signal.When you put on the heart rate monitor, it beginstransmitting heart rate data plus a unique, randomly-selected code. When you turn on the Forerunner, it begins“listening” for data from the heart rate monitor. Once theForerunner “hears” two or more transmissions of heart ratedata that contain the same unique code, it pairs with theheart rate monitor, creating a unique wireless link.Once paired, the Forerunner will never receive conflictingsignals from another heart rate monitor, so you can exercisein close proximity to other heart rate monitors withoutfear of interference. If the Forerunner loses your heart ratesignal, the pairing process begins again automatically.Follow these steps to pair successfully with your heart ratemonitor:• Position the heart rate monitor and establish a strongconnection between it and your pulse.• Position the Forerunner within range of the heart ratemonitor (90–110 cm or 35–43 in).• Stand at least six feet away from any other heart ratemonitor (only while pairing).InterferenceStrong electromagnetic fields can interfere withcommunication between your heart rate monitor and yourForerunner. Common sources of interference include highvoltage power lines, electric motors, computers, televisions,and mobile phones. Interference may cause your heart rateto appear unusually high, freeze, or disappear. Once youmove away from the source of interference, your heart ratereading should return to normal.