What is the name of the signal that electrically reports engine speed?

The correct answer is the tachometer signal, which is a specific type of electrical signal that measures and reports the engine's rotations per minute (RPM). The tachometer is a device that converts this RPM information into a readable format, often displayed on the vehicle's dashboard. This signal is essential for monitoring engine performance and ensuring it operates within optimal RPM ranges.

The RPM signal may seem similar, but it is more of a description of what the tachometer measures rather than the actual signal itself. While engine frequency signals could also relate to RPM, they typically pertain to the broader context of frequency in signal processing. The speedometer signal is concerned with vehicle speed rather than engine speed, making it irrelevant in this context.