A walkie-talkie was a handheld communication device, a type of portable two-way radio.
On Vortis, when the First Doctor picked up a distress signal on his radio, he used the walkie-talkie's directional aerial to track its source. (PROSE: The Lair of the Zarbi Supremo)
In 1968, Christine Cooper gave the Seventh Doctor a walkie-talkie. (PROSE: Nightshade)
UNIT used them in the 2000s. (TV: The Sontaran Stratagem/The Poison Sky)
They were used by members of the Silver Cloak. (TV: The End of Time)
Walkie-talkies were used by employees at the Harries & Harries headquarters. (TV: Meat)