Definition
A scalable air traffic control communications system used at terminal facilities (such as control towers and TRACONs) that provides controllers with the voice communication equipment needed to talk with pilots and coordinate with other ATC facilities. Built on a modular design, it can be configured and expanded to match the size and traffic demands of the facility it serves.
Plain English
It's the radio and intercom system controllers use in a tower or approach control room. 'Modular' means it can be built up in pieces, so a small tower gets a small setup and a busy approach control gets a much larger one.
Context Anchor
Seen in FAA acronym lists and in discussions of air traffic control communications equipment, especially equipment used by towers and airport-area control facilities.
Derivation
Modular' comes from the Latin modulus, meaning 'a small measure' — referring to standard-sized building blocks that can be combined. 'Terminal' here means the airport/approach environment (the start and end points of flights), not the en route phase. So the name describes a building-block communications system for the terminal ATC environment.
Why Pilots Care
Pilots normally do not operate MTCS, but if this equipment has a problem, controller radio communications in the airport area may be affected.
Intuition Check
Do not read terminal here as the passenger building at an airport. In this term, terminal means the air traffic control environment around an airport.
Example Sentence 1
The tower's MTCS allows the local controller to transmit on the tower frequency while simultaneously coordinating with approach control on a separate line.
Example Sentence 2
Maintenance checked the MTCS modules after a reported communications dropout at the ramp.