The cell phone is a complex radio device with a simple function: communication. To provide voice, text and data services, manufacturers must work dozens of important parts into a small space. The end result is a small but sophisticated machine -- a handheld computer -- that offers several of the same functions as older, more costly electronic devices that are rapidly becoming obsolete.
The circuit board holding microchips and processors inside a cell phone serves as the brains of the outfit. A digital signal processor, or DSP, converts an analog signal -- your voice -- to digital for transmission through the provider's network. The DSP also converts a received digital signal to analog and moves the analog to the phone's speaker and your ear. Radio frequency transmitters and receivers handle the signal as it moves to and from the phone. A microprocessor on the circuit board controls the phone's various other functions, such as the keyboard and display. The phone's operating system works from a memory chip, and the power management system keeps the device operating under battery power. A baseband chip serves as the phone's antenna, grabbing and emitting digital signals when the phone is in use.
Microphones, Cameras and Speakers
Cell phone microphones perform the same function as any other microphone, although they do it in a much smaller space. Microphones go live when the phone powers up and are actively listening whenever the power is on, even if there's no call in progress. That's why it's possible to hack into a phone, surreptitiously turn it on and record anyone speaking in the vicinity. It has also become possible for hackers to track a cell phone's location, intercept voice calls and texts, copy address books and activate the camera without the user's knowledge.
Cell phone batteries provide power and take up most of the space inside the device. At one time, all cell phones allowed their batteries to be easily removed and replaced by allowing access to the interior. More recent devices such as the iPhone have embedded batteries that are not designed for replacement. This attribute makes sealed covers and a slimmer, smoother and more contoured design possible for the manufacturer.
A cell phone identifies its user with a subscriber identification module, or SIM, card. The card carries information associated with the individual user, such as her phone number, address book and other personal data, such as text messages. SIM cards, which are necessary for the phone to work, can be switched between phones, allowing a user purchasing a new model to easily install essential information on the replacement.
LCD and Keyboard
For techies who design and repair cell phones, the exterior surfaces of the device are known as back and front fascia. On the front fascia, every cell phone has a display screen as well as a keyboard, which may be integrated into the display. A speaker (or "ringer") is positioned at the top of the phone and a microphone at the bottom. The exterior has an on/off switch and inputs for charger cords and useful attachments such as headsets. The back fascia, on some models, allows access to the interior fascia, which is the structural skeleton of the device, holding the board and the miscellaneous electronic components such as the vibrator, the light-emitting diode (LED), charging and headphone connectors and memory card.