HEART RATE MONITOR
Precise measurement/ANT+ BLE/Bike computers&Smart phone
The electrical monitors consist of two elements: a monitor/transmitter, which is worn on a chest strap, and a receiver. When a heartbeat is detected a radio signal is transmitted, which the receiver uses to display/determine the current heart rate. This signal can be a simple radio pulse or a unique coded signal from the chest strap (Bluetooth, ANT+).
Devices use optics to measure heart rate by shining light from an LED through the skin and measuring how it scatters off blood vessels.