Complex sentence: Telescreens do not have night vision technology, thus, they cannot surveil in the dark; this is compensated by the fact that telescreens are incredibly sensitive, and can pick up a heartbeat.
Split into simpler sentences: Telescreens do not have night vision technology, thus, they cannot surveil in the dark. This is compensated by the fact that telescreens are incredibly sensitive, and they are said to pick up a heartbeat.