Alarm clock, a necessary device in our daily lives, has different synonyms based on the purpose it serves. A wake-up alarm clock is also known as a "timepiece" or a "wake-up timer," which helps people wake up in time for work or other commitments. A travel alarm clock, also called a "portable alarm clock," is a small-sized alarm clock that people carry while traveling. People who have trouble waking up might use a "clock radio," which plays radio music or sounds along with the alarm. A more traditional type of alarm clock is the "pendulum clock," which keeps time using a swinging pendulum. Other terms for the alarm clock include "timepiece," "alarm timepiece," "clock with alarm function," and "automatic wake-up timer".