What special type of altimeter is used to send pressure altitude to air traffic control?

The encoding altimeter is specifically designed to convert pressure altitude into an electrical signal that can be transmitted to air traffic control (ATC). This process is essential for ensuring that ATC has accurate flight level information as part of its traffic management and safety protocols.

The encoding altimeter measures the atmospheric pressure and translates this measurement into an altitude reading, which is then encoded into a digital format suitable for transmission. This capability allows for accurate tracking of aircraft altitude in relation to the standard pressure reference used in aviation operations.

In contrast, a standard altimeter, pressure altimeter, and digital altimeter may provide altitude information but lack the functionality to encode this data for transmission to ATC. Thus, they do not meet the specific need of providing altitude data in a format that is directly usable by air traffic controllers for managing air traffic safely.