A voltage signal refers to an electrical signal that carries information in the form of varying voltage levels. It is a way of transmitting data or conveying messages using different voltage values. Full definition
The sensor element then sends voltage signals... (carid.com)
The thing that surprises me is the very low voltage signal, because the engine coolant temperature shows that the engine is quite warm (which it should be after 9 minutes of running at 4000 RPM), so regardless of the O2 heater malfunction that lambda sensor should be hot and triggering the ECU to run in closed loop (which it clearly isn't). (mechanics.stackexchange.com)
Computer monitors radiate low - voltage signals from their power cords which allow people with sophisticated monitoring equipment to capture and reassemble the images on your monitor. (lawyerist.com)