How to detect different physiological signals automatically?

Hi,

I am writing a code that can recognize some physiological signals such as ECG, PPG and EMG automatically. For this purpose, I need to extract some features from each signal and then learn them to a neural network.

My problem is at features selection part. Which features for each signal should be extracted that can be useful in automatic detection process of these signals?

I appreciate your help in advance.

-BR, Shadi