Outputs Digital pulse for calculation by external microcontroller to derive BPM.
Heart beat sensor is designed to give digital output of heat beat when a finger is placed on it. When the heart beat detector is working, the beat LED flashes in unison with each heart beat. This digital output can be connected to microcontroller directly to measure the Beats Per Minute (BPM) rate. It works on the principle of light modulation by blood flow through finger at each pulse.
For further information please refer to its datasheet.
Output checking on scope for reference below. The output is digital level at around 5V supply. The duration between pulses are used to calculate the heart beat.