How Cellphone Works Quiz

FDMA separates the spectrum into distinct voice channels by splitting it into uniform chunks of bandwidth. To better understand FDMA, think of radio stations: Each station sends its signal at a different frequency within the available band. FDMA is used mainly for analog transmission. While it is certainly capable of carrying digital information, FDMA is not considered to be an efficient method for digital transmission.

On 3 April 1973 when Martin Cooper, a Motorola researcher and executive, made the first mobile telephone call from handheld subscriber equipment, placing a call to Dr. Joel S. Engel of Bell Labs.

Both walkie-talkies and CB radios are half-duplex devices. That is, two people communicating on a CB radio use the same frequency, so only one person can talk at a time.

TDMA is the access method used by the Electronics Industry Alliance and the Telecommunications Industry Association for Interim Standard 54 (IS-54) and Interim Standard 136 (IS-136). Using TDMA, a narrow band that is 30 kHz wide and 6.7 milliseconds long is split time-wise into three time slots.

CDMA takes an entirely different approach from TDMA. CDMA, after digitizing data, spreads it out over the entire available bandwidth. Multiple calls are overlaid on each other on the channel, with each assigned a unique sequence code. CDMA is a form of spread spectrum, which simply means that data is sent in small pieces over a number of the discrete frequencies available for use at any time in the specified range. Verizon, Sprint and most other U.S. carriers use CDMA, which means no SIM card.

When the Apple iPhone hit the market, it was a locked phone -- it worked only with AT&T service. But inventive users quickly found hacks that could bypass the lock, making their phones usable on other networks.

GSM (Global System for Mobile Communications, originally Groupe Spécial Mobile), is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe the protocols for second-generation (2G) digital cellular networks used by mobile phones, first deployed in Finland in July 1991.As of 2014 it has become the default global standard for mobile communications - with over 90% market share, operating in over 219 countries and territories

A Digital Signal Processor (DSP) is a highly specialized processor designed specifically for performing signal manipulation calculations at high speed. It is commonly used in cellphones and other devices that require real-time processing of audio, video, and other signals. DSPs are optimized for tasks such as filtering, encoding, decoding, and compressing signals, making them ideal for applications where fast and efficient signal processing is necessary.

The correct answer is System Identification Code. The System Identification Code is a unique 15-bit number that is assigned to each carrier by the Federal Communications Commission (FCC). It is used to identify and differentiate carriers within the telecommunications network. The System Identification Code helps in managing and regulating the communication services provided by different carriers.

The Mobile Identification Number (MIN) is a 10-digit number that is derived from your phone's number. It is a unique identifier assigned to mobile devices, allowing them to be recognized and authenticated on a cellular network. The MIN is used for various purposes such as routing calls, tracking usage, and identifying the device for billing and security purposes.

Many digital cellular systems rely on frequency-shift keying (FSK) to send data back and forth over AMPS. FSK uses two frequencies, one for 1s and the other for 0s, alternating rapidly between the two to send digital information between the cell tower and the phone. Clever modulation and encoding schemes are required to convert the analog information to digital, compress it and convert it back again while maintaining an acceptable level of voice quality. All of this means that digital cell phones have to contain a lot of processing power.

A typical large city can have hundreds of towers. But because so many people are using cell phones, costs remain low per user. Each carrier in each city also runs one central office called the Mobile Telephone Switching Office (MTSO). This office handles all of the phone connections to the normal land-based phone system and controls all of the base stations in the region.

ROM stands for Read-Only Memory, which is a type of storage in a computer or electronic device that permanently stores data. In the context of a phone, ROM provides storage for the phone's operating system and customizable features, such as the phone directory. Unlike RAM (Random Access Memory), ROM retains its data even when the device is powered off. This allows the phone to boot up and run essential functions smoothly. Therefore, ROM is the correct answer as it explains the storage function of the phone's operating system and customizable features.

A version of AMPS known as Narrowband Advanced Mobile Phone Service (NAMPS) incorporates some digital technology to allow the system to carry about three times as many calls as the original version. Even though it uses digital technology, it is still considered analog. AMPS and NAMPS only operate in the 800-MHz band and don't offer many of the features common in digital cellular service, such as e-mail and Web browsing.

The correct answer is Electronic Serial Number. The explanation is that a unique 32-bit number is programmed into the phone when it is manufactured, and this number is known as the Electronic Serial Number. It serves as a unique identifier for the phone and is used for various purposes such as tracking, authentication, and activation of the device.

The signals from each tower don't travel far beyond their range of 10 square miles. This means that cellular providers can use the same frequencies over and over in different cells, so more people can talk at the same time.
25 square miles (65 square kilometers)

Old school: DynaTAC cell phone, 1983
PHOTO COURTESY MOTOROLA, INC.
In 1983, the analog cell phone standard called AMPS (Advanced Mobile Phone System) was approved by the U.S. Federal Communications Commission (FCC) and first used in Chicago. AMPS uses a range of frequencies between 824 megahertz (MHz) and 894 MHz for analog cell phones. In order to encourage competition and keep prices low, the U. S. government required the presence of two carriers in every market, known as A and B carriers. One of the carriers was normally the local-exchange carrier (LEC), a fancy way of saying the local phone company.

You might imagine the cell phone network as blanket of radio waves spread over a large region. It's really more like a quilt made of small, hexagonal areas called cells. Each cell has its own tower and base station.

If you're talking on a digital phone over a digital network, your voice becomes a stream of 1s and 0s. These 1s and 0s take up a lot less room than an analog signal, which is a constantly varying wave of information.