GSK 783 were the call letters of the private transmitter owned by George Samuel Kirk when he lived on Deneva in 2266. His brother, James T. Kirk, ordered Uhura to signal this transmitter when she failed to receive a response from an official transmitter. When she did, George's wife, Aurelan, responded briefly, begging for help, then abruptly severed contact (TOS: "Operation -- Annihilate!" )