Chambers coil

From Memory Alpha, the free Star Trek reference.

The chambers coil is a component found aboard 23rd century Federation starships whose malfunction can cause an overload to a ship's communications system.

During the USS Enterprise's initial contact with the USS Reliant, which was commandeered by Khan Noonien Singh, Lieutenant Uhura received a message stating that the Reliant's "chambers coil is overloading their comm system." However, when Spock scanned the Reliant, he discovered that their coil emissions were normal, indicating that the Enterprise was being deceived. (Star Trek II: The Wrath of Khan)