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Mobile telephone. Blank LCD (liquid crystal display) screen on a mobile telephone. The aerial (top centre) strengthens incoming and outgoing signals that transmit voice and other data to the communications network. Mobile phones transmit and receive this data using low-intensity microwaves. Voice data is converted to sound waves and emitted from the speaker (holes, upper left). Two command buttons and a scroll wheel (lower centre) are used to control the phone, and an on/off switch (upper right) to control power from the battery. The keypad is hidden by a removable cover. This model is manufactured by Nokia. (KEYSTONE/SCIENCE PHOTO LIBRARY/TON KINSBERGEN)