Cellular telephones offer many features and options, including

• Voice activation Sometimes called “hands-free operation,” this feature allows the user to establish and answer calls by issuing verbal commands. This safety feature enables a driver to control the unit without becoming visually distracted.
• Memory functions These allow storage of frequently called numbers to simplify dialing. Units may offer as few as 10 memory locations or in excess of 100, depending on model and manufacturer.
• Multimode This allows the phone to be used with multiple carriers. The phone can be used to access digital service where it is available and then switch to an analog service of another wireless carrier when roaming.
• Multiband This allows the phone to be used with multiple networks using different frequency bands. For example, the cell phone can be used to access the 1900-MHz band when it is available and then switch to the 800- MHz band when roaming.
• Visual status display This conveys information on numbers dialed, state of battery charge, call duration, roaming indication, and signal strength. Cell phones differ widely in the number of characters and lines of alphanumeric information they can display. The use of icons enhances ease of use by visually identifying the phone’s features.
• Programmable ring tones Some cellular phones allow the user to select the phone’s ring tone. Multiple ring tones can be selected, each assigned to a different caller. Avariety of ring tones may be downloaded from the Web.
• Silent call alert Features include visual or vibrating notification in lieu of an audible ring tone. This can be particularly useful in locations where the sound of a ringing phone would constitute an annoyance.
• Security features These include password access via the keypad to prevent unauthorized use of the cell phone as well as features to help prevent access to the phone’s telephone number in the event of theft.
• Voice messaging This allows the phone to act as an answering machine. Alimited amount of recording time (about 4 minutes) is available on some cell phones. However, carriers also offer voice-messaging services that are not dependent on the phone’s memory capacity. While the phone is in standby mode, callers can leave messages on the integral answering device. While the phone is off, callers can leave messages on the carrier’s voice-mail system. Users are not billed for airtime charges when retrieving their messages.
• Call restriction This enables the user to allow use of the phone by others to call selected numbers, local numbers, or emergency numbers without permitting them to dial the world at large and rack up airtime charges.
• Call timers These provide the user with information as to the length of the current call and a running total of airtime for all calls. These features make it easier for users to keep track of call charges.
• User-defined ring tones These offer users the option to compose or download ring tones of their choice to replace the standard ring tone that comes with the cell phone.
• Data transfer kit For cell phones that are equipped with a serial interface, there is software for the desktop PC that allows users to enter directory information via keyboard rather than the cell phone keypad. The information is transferred via the kit’s serial cable. Through the software and cable connection, information can be synchronized between the PC and cell phone, ensuring that both devices have the most recent copy of the same information.