Wrist communicator

A Wrist communicator was a form of communication or a device, which could be attached to the wrist in order for easy discussion.

Appearances
The First Doctor provided himself with one in 1900 London in order to receive a message from his granddaughter Susan Foreman in the TARDIS. He later realised, after receiving a number of messages from his granddaughter, that while visiting Aldridge, the Doctor had been in a blocked-signal field, which prevented him from receiving the messages. (A Big Hand for the Doctor)