A pager was a type of text-based communications device used on Earth during the late 20th century. This device alerted its user to a recently received message by beeping, and were used by people who needed to be contacted quickly, such as doctors. Due to where they were usually stored on a person, some people referred to these devices "pocket pagers".
In 1986, while at an Italian restaurant for dinner, James T. Kirk's communicator beeped several times. Surprised by the interruption, his dining companion, Doctor Gillian Taylor, asked him if he was a doctor. (Star Trek IV: The Voyage Home)