Definition
An electronic unit that both sends out (transmits) radio signals and receives the returning signals, processing them into usable information for the aircraft's avionics. In a radio altimeter system, the RT generates the signal sent toward the ground from the transmit antenna, then receives the reflected signal at the receive antenna and measures the time delay to calculate height above the surface.
Plain English
A single box that both sends a radio signal out and listens for it coming back. In a radio altimeter, it bounces a signal off the ground and uses the return to work out how high the aircraft is.
Context Anchor
Seen in radio altimeter system diagrams, where the RT unit connects with the radio altimeter antenna and the cockpit height display.
Derivation
Built from two plain English words: receiver (the part that listens for incoming signals) and transmitter (the part that sends signals out). Combining them into one term reflects that both functions live in the same physical unit.
Why Pilots Care
It supplies continuous, terrain-referenced altitude data essential for safe low-altitude operations and instrument approaches.
Analogy
It is like one device that both calls out and listens for the echo. The radio altimeter RT does that with radio signals aimed at the ground.
Intuition Check
Do not read RT here as a pilot talking on the radio. In this context, it is a radio altimeter component that sends and receives signals to help measure height above the ground.
Example Sentence 1
The radio altimeter's receiver-transmitter sends a signal down through the transmit antenna and measures how long the reflected signal takes to return.
Example Sentence 2
During the approach the pilot cross-checks the radio altimeter readout generated by the RT against the barometric instruments.