Call sign
From Tardis Wiki, the free Doctor Who reference
Space Station W3 used the call sign LX88J. (TV: The Wheel in Space)
The Intrusion Counter-Measures Group used call signs such as Red Four, used by Rachel Jensen; Red Six, used by a van driven by Mike Smith; Red Nine, Blue One, Blue Four and Blue Six. (TV: Remembrance of the Daleks)
The Brigadier and other members of UNIT often used variations of Greyhound and Trap as call signs (TV: The Mind of Evil, The Claws of Axos, etc.)
