Strong 3MHz probe for a clearer sound output Powerful built-in speaker for listening the heartbeat without headphones Color LCD 160X128 pixel Red-alarm feature which indicates the heartbeats are getting out of range to indicate adjustments. Uses 2 AA size batteries which are easy to find (2 new batteries are included)- 2 batteries are enough for 15 hours or continuous service Auto-off feature & low battery consumption to ensures hours & hours of usage Battery icon which indicates how much battery is left Headphone jack for listening to the heartbeat Compact design with buttons which are design to withstand repeated usage without wearing out or breaking Light and very easy to handle 3 work modes: real-time FHR display mode, averaged FHR display mode, and manual mode . The FHR can also be displayed in waveform Auto switch-off Three Modes Mode 1: a heart icon is displayed when the heartbeat is detected and the real-time hear t rate is displayed numerically. Mode 2 : a heart icon is displayed when the heartbeat is detected and it averages the heart rate for a more stable reading. Mode 3 : this mode allows the user to calculate an average heart rate over a specific period of time by manually pushing a button to start & stop the time.