The codename Tinsel referred to a type of equipment carried by RAF bombers and used for jamming Luftwaffe night-fighter controllers' speech radio-frequencies during the Second World War. The equipment consisted of an audio microphone mounted inside one of the bomber's engine nacelles, the output of which fed into the aircraft's standard radio transmitter. The wireless operator could listen in to the frequencies used by the defending forces and then, when he heard a German transmission, tune his transmitter into the Luftwaffe frequency and transmit the amplified engine-noise on the same frequency, thus jamming the enemy transmission.