IN THE EARLY 1990s, THE CELLPHONE (or mobile phone) was a rare luxury, but in recent years it has outsold almost every other electrical gadget— as a professional tool, domestic convenience, and even a fashion accessory. Cellphones have also generally shrunk in size, due to improvements
in rechargeable batteries, which now store more electricity for longer in a smaller package, and to smaller, more efficient electronics that use less electricity. A “cellphone” is basically a low-power
radio receiver-transmitter, plus a tiny microphone to convert sounds into electrical signals, and a small speaker that does the reverse. When the cellphone is activated, it sends out a radio signal that
is answered by nearby mast transmitter -receivers. The phone locks onto the clearest signal and uses
this while within range (the range of each transmitter is known as a cell). The phone continuously monitors signal strength and switches to an alternative transmitter when necessary. The phone’s liquid crystal display (LCD) shows numbers, letters, symbols, and color pictures. Newer models have a larger screen for more complex color images, and commonly incorporate a camera, radio, and MP3 functionality. Smartphones, which are increasingly widespread, contain additional software and more may be downloaded. Smartphones typically offer internet and email access, PDA-like functions, and may even contain GPS navigation software.
