Answer : The electrocardiogram records the electrical signals of heart.
Explanation :
Electrocardiogram : It is a type graph that records the electrical signals or rate of the heart. It is also called ECGs.
It is a common test that is used to detect the problems in heart and also monitor the status of the heart in many conditions.
During the ECG, sensors (electrodes) that can detect the electrical activity of the heart are attached to the chest.
Hence, the type of data recorded by the electrocardiogram is the electrical signals of heart.