Understanding the mobile phone
The number of mobile phone users is expanding phenomenally. Experts call it a mobile revolution. People from all walks of life, of all ages use them. They carry it in their hands, pockets or purses. One can find advertisements related to cell phones anywhere: roads, newspapers, and television. Once considered a luxury item it is becoming the gadget for masses. Theoretically a person carrying a mobile (cell phone) can be in contact anywhere, anytime.
But few are aware of the technology that makes it possible. It is not very difficult to become aware of its nitty-gritties.
How it works
To use a cell phone one needs a handset. The handset of a cell phone, as you might have seen, has a small screen at one end and a panel of buttons below it. Some handsets have a small antenna that is protruding out from its, but it is not universal. Some modern handsets are foldable so that when not in use the panel of buttons is not visible, these handsets have a larger screen that can display colour pictures also.
The essential component of the technology that make cell phone possible are networks of a large number of radio transmitters/receivers. Each cell phone company has a network of this kind that is controlled in each city/state by its central office known as MTSO (Mobile Telephone Switching Office) . You know that our body is made up of many cells. These networks are also cellular akin to the body of any animal. The area covered by a cell phone company, a city or a state, for its services is divided into zones that are called its cells. Thus the network of a cellular company is made up of many such cells. Each of these cells has a moderately sized radio transmitter/receiver and a microprocessor based instrument somewhat like a computer, located at a place known as its base station. Base stations can communicate with each other. They can easily located in a town/city because of the prominent size of their antenna above some buildings.
The Electromagnetic Waves
The form of energy transferred from one point to another at a speed of about 300,000 kilometers per second –the speed of light --, is called electromagnetic radiation. It is of several kinds. It can be visualized to spread like a wave. Therefore electromagnetic radiations are also called electromagnetic waves.
The distance between two adjacent crests of a wave is called its wavelength. The shorter the wavelength, the more energetic is the wave. Wavelength is also related to the frequency of a wave. Frequency is expressed in the units of Hertz, kilohertz (KHz) and megahertz (MHz). Other than wavelength, frequency and energy there is no difference between different kinds of electromagnetic radiations: radio waves, X-rays, microwaves and light. Radio waves are waves used for telecommunication
Electromagnetic waves in the radio frequency (RF) range can be divided into several ‘bands of frequencies’. Different bands that are allocated for different uses e.g. radio, television, aircraft communications, satellites, mobile phones and pagers. The band 0.5 – 1.7 megahertz (MHz) is allocated to conventional radio stations. Similarly the band 470 –750 MHz is allocated for TV transmission.
The bands of radio frequency allocated for use by cellular phone operators is 800 –900 MHz and 1800-1900 MHz.
A cell phone handset is also a low power radio transmitter/receiver. It can transmit as well as receive electromagnetic waves from its closest base station when it is powered on.
As soon as one turns on a cell phone handset it listens for SID (System Identification Code - a unique 5-digit number that is assigned to each carrier by the central authority say TRAI (Telecom Regulatory Authority of India) and is programmed into each handset when it is activated by a company.) on the control channel. The control channel is a special frequency that the phone and base station use to talk to one another about things like call set-up and channel changing. If the phone cannot find any control channels to listen to, it knows it is out of range and displays a "no service" message. The SID helps a cell phone company to identify cell phone handsets registered with it that are powered ON.
It also transmits a signal that includes the ESN to the base station of its parent company every few seconds. The computers attached to these transmitters/receivers maintain latest information about all the handsets distributed/registered by the parent company. This information at each base station is constantly updated. Thus base station of each cell knows the location of every powered on handset at any instance of time, through the codes SID and ESN.
When one dials a number on a handset signals are first converted into electricity and then into electromagnetic waves that are transmitted by it. The radio receiver of the cell in which handset is located at that time receives this signal. It is in then communicated to its computer to find the nature of the addressed party. If it is addressed to another cell phone serviced by the parent company, it finds out the location of the addressed handset and transmits signals to that base station, which in turn alerts the handset about the incoming call.
In case the call is addressed to a cell phone serviced by another company or to a landline telephone the cell directs the call into relevant network, which then directs the call in a similar fashion.
If a handset moves toward the edge of a cell, the cell's base station senses that the strength of the signals from that handset is diminishing. Meanwhile, the base station in the cell towards which it is moving (because is also listening and measuring signal strength on all frequencies) sees that the strength of radio waves from it is increasing. The two base stations coordinate with each other through the MTSO, and at some point, the handset gets a signal on a control channel telling it to change frequencies. Thus the handset is switched to the new cell.
If the handset moves to another city/state the SID on the control channel does not match the SID programmed into the handset. If the cellphone company provides roaming facility then the phone knows it is roaming. The MTSO of the cell that you are roaming in contacts the MTSO of the home system, which then checks its database to confirm that the SID of the phone you are using is valid. Your home system verifies your phone to the local MTSO, which then tracks your phone as you move through its cells. The amazing thing is that all of this happens within seconds!
Cell Phone Companies
Cell phone services are often offered by a number of companies . They are known as cell phone service providers. Each one of them has a network of its own to provide services in a limited region.
SID and ESN
All cell phones have special codes associated with them. There is a phone numbers allocated to each cell phone user. In India these numbers have 9 as their first digit. Then there are other code numbers that are used to identify the phone, the phone's owner and the service provider. SID (System Identification Code) is a unique 5-digit number that is assigned to each cell phone company by the government. When a cell phone is switched on, it listens for an SID on the control channel. The control channel is a special frequency that the phone and base station use to talk to one another. If the phone cannot find any control channels to listen to, it knows it is out of range and displays a "no service" message. When it receives the SID, the phone compares it to the SID programmed into the phone. If the SIDs match, the phone knows that the cell it is communicating with is part of its parent company..
Electronic Serial Number (ESN) is a unique 32-bit number programmed into the phone when it is manufactured.
Inside a handset
A cell phones handsets is somewhat like a palmtop computer. It is the most intricate device common people play with daily. But, if you were to take a cell phone apart, you will be surprised to discover very few parts inside it. They are:
A circuit board that has several chips (IC’s) on it.
An antenna
A liquid crystal display (LCD)
A keyboard (not unlike the one you find in a TV remote control)
A microphone
A speaker
A battery
Let us explore the function of each one of them. One chip on the circuit board translates the sound that is spoken near the microphone from analog to digital and the incoming digital signal back to sounds that can be heard through its speaker. Cell phones have such tiny speakers and microphones that it is incredible how well most of them reproduce sound. As you can see, the speaker is about the size of a 25p coin and the microphone is even smaller. The keyboard allows the user to enter information like the telephone number etc.
Digital or Analog: Electrical signals can be of two kinds, continuous or discrete. Electrical signals generated from sound by a microphone are of continuous kind. Such signals are known as analog signals. Signals that are used inside and between computers are made up of bursts of electrical current. They are known as digital signals.
Another chip on the circuit board, known as the microprocessor, handles all of the housekeeping chores for the keyboard and display. It deals with command and control signaling with the base station and also coordinates the rest of the functions on the board. Then there are some memory chips on the circuit board, which enable the cell phone to remember. A cell phone has to carry out many preprogrammed instructions. Therefore it has to remember all them. Memory is also essential for many other tasks a cell phone is useful for. The antenna is required to receive and transmit radio frequency (RF) signals. The rechargeable battery provides energy for all these functions.
History
The genesis of cellular phones can be traced back to 1947, when some engineers in USA looked at crude mobile (car) phones and realized that by using small cells (range of service area) with frequency reuse they could increase the traffic capacity of mobile phones substantially. However at that time, the technology to do so was nonexistent.
In USA, anything to do with broadcasting and sending a radio or television message out over the airwaves is decided by a department known as Federal Communications Commission (FCC). Since a cell phone is a type of two-way radio, in 1947, an American company AT&T proposed that the FCC allocate a large number of radio-spectrum frequencies so that widespread mobile telephone service would become feasible. But FCC declined this request.
The FCC reconsidered its position in 1968. AT&T and another well-known American company ‘Bell Labs’ then proposed the present form of cellular system. In this system many small, low-powered, broadcast towers, each covering a 'cell' a few miles in radius collectively cover a large area. Each tower uses only a few of the total frequencies allocated to the system. As the phones travel across the area, calls are passed from tower to tower.
Dr Martin Cooper, a general manager at an American company ‘Motorola’, is considered the inventor of the first modern portable handset. Cooper made the first call on a portable cell phone in April 1973. He made the call to his rival, Joel Engel. Thus Motorola was the first company to incorporate technology into portable device that was designed for use even outside of an automobile. By 1977, AT&T and Bell Labs had constructed a prototype cellular system.
Landline, GSM and CDMA
Conventional phones that are connected to one another largely through wires on the land are known as landline phones. Till very recently such phone service in India was provided only by government agencies like MTNL or BSNL. The technologies used for such telephones are rather ancient – more than fifty years old.
Cellular phones on the other hand had to overcome a major hurdle to become popular. Within a band of radio frequency, no two transmissions can use the frequency - at the same time. Therefore the number of people that can communicate using a band of frequencies is very limited. Cell phones therefore use technologies that have been developed in the last two decades only. GSM and CDMA are the names of two technologies that are most widely used by cellular companies in India. These are the technologies that enable a large number of people to communicate with one another using a very limited band of frequencies
GSM is an acronym for Global System for Mobile Telecommunications; cellular companies like AirTel, Hutch, Idea use this technology to provide their services. This technology is older then CDMA. In this technology mobile phones convert voices into a series of on-or-off electrical pulses, which are relayed in short bursts as packages of data. GSM is efficient because in the intervals between bursts, other phones can also send packets of data: in this way, this digital technology enables up to eight conversations to be held on the same channel virtually simultaneously.
CDMA is the acronym for the more recent technology called Code Division Multiple Access. CDMA takes an entirely different approach from GSM. Therefore handsets that are used for GSM services cannot be used for CDMA and vice versa. At present the major cellular companies in India that provide services using this technology are Reliance, Tata, and MTNL. In this technology, a spoken word or sentence from a user is first digitized, that is converted into electrical pulses like in GSM. But these pulses are coded and transmitted using the entire range of frequencies after ascribing them a particular code. At the receiving end they are combined together through the same code to generate the original word/sentence. This entire process occurs so fast that we cannot detect it.
The very many uses of Cell phone Handsets
A cell phone handset is useful not only for talking to people, it can be used for several other useful tasks too.
As a phonebook, diary, alarm timepiece
People often need to remember telephone numbers of their acquaintances, to use a telephone. Most cell phones today can store more than a hundred telephone numbers. The names can be displayed in alphabetical order on the screen. As soon as one clicks a button when a pointer on the screen points to a particular name, telephone number associated with it gets displayed on the screen and one can dial that number by just pressing another button. A cell phone handset also keeps record of recently dialed, received and missed calls, so that they can be dialed instantaneously.
One can use a cell phone as a personal diary also. A cell phone can be used to store information about dates important for its user or to keep information about future appointments. It can also alert its owner at a particular time on a particular day.
Send and receive text messages
Cell phones are useful not only for talking; one can also send short messages through them. These messages are called SMS (short messaging service). One can type in the text message with the same keys used for entering a phone number before dialing. Sending SMS is especially useful when you are not sure that the person to whom you want to convey the message may be immediately ready to receive it personally. An SMS message is stored in the handset and can be read anytime. This facility is becoming very popular because through it one can receive useful/interesting information almost anytime anywhere.
Voice Mail
The voice mail facility is very useful if one does not want to be disturbed by a telephone call but also does not want to miss any urgent message. In this facility the message is recorded and kept stored in the computers of the parent company. The user can access these messages whenever s/he wants to.
A camera or a sound-recorder
Certain handsets have a small camera built into them. With the help of this camera one can take pictures of a person or place around him and then instantly send it to some one who has a similar handset. Similarly some handsets have the facility to record sounds and play them at one’s own convenience.
Play games
A cell phone accompanies its owner almost everywhere, so manufactures of handsets have found an interesting application of the handset when one is getting bored. Cell phone handsets can be used to play some games when one is traveling or is alone. Such games can be downloaded from several vendors using the cell phone services. The games are especially interesting in the modern handsets that have a multicolor display.
As a calculator
Some cell phone handsets can also be used for small calculations useful for its owner in daily life. This is possible because the handset has a keyboard and a display screen just like a calculator.
Access Information on the Internet
Traditionally to access information one needs a computer and a telephone. A Cell phone handset has a microprocessor just like a computer and it is just like a telephone with a screen. It is therefore not very surprising that on certain handsets some cell phone companies are offering their clients the Internet services on their cell phone. An owner of such a handset can browse through the Internet almost like on a laptop computer.
Cell phone Etiquette
While using a conventional landline phone one is either at home or in a office, where are people around you are your relative or acquaintances. With a cell phone this is not always true. One may receive a telephone call anywhere and the alarm bell when one receives a call and the talk can disturbs people around. It is therefore necessary that people using cell phones should observe social etiquette. Here are a few do’s and don’t for cell phone users.
While riding public transport, one must try to avoid loud and eccentric conversations by keeping one’s voice low or to a relaxed, normal level. One must avoid extensive phone calls. There is a rule of thumb when talking on a cell phone and that is to maintain at least a 3 metre zone from anyone while talking.
One must keep ringer volume to a minimal. One can be less intrusive by using the silent or vibration options available on the handset. One can also set one’s cell phone to voice mail when it's inappropriate to take a call.
While attending public gatherings one must not interrupt by letting the sounds of one’s cell phone ringing. The sounds of a cell phone ringing are often very irritating for people around in a movie hall or a restaurant. One must avoid talking on cell phones while inside a theater, a library, a museum, or other enclosed community spaces, such as hospital emergency room.. If one has to make a call, one must make sure to take it to another area where the disruption to other people would be less.
One must always follow the rules about cell phone use in hospitals or on airplanes. These places have their own type of radio waves and outside interference such as a cell phone could interfere with the signals or other sensitive equipment. One must adhere to all posted signs and instructions in such places.
But few are aware of the technology that makes it possible. It is not very difficult to become aware of its nitty-gritties.
How it works
To use a cell phone one needs a handset. The handset of a cell phone, as you might have seen, has a small screen at one end and a panel of buttons below it. Some handsets have a small antenna that is protruding out from its, but it is not universal. Some modern handsets are foldable so that when not in use the panel of buttons is not visible, these handsets have a larger screen that can display colour pictures also.
The essential component of the technology that make cell phone possible are networks of a large number of radio transmitters/receivers. Each cell phone company has a network of this kind that is controlled in each city/state by its central office known as MTSO (Mobile Telephone Switching Office) . You know that our body is made up of many cells. These networks are also cellular akin to the body of any animal. The area covered by a cell phone company, a city or a state, for its services is divided into zones that are called its cells. Thus the network of a cellular company is made up of many such cells. Each of these cells has a moderately sized radio transmitter/receiver and a microprocessor based instrument somewhat like a computer, located at a place known as its base station. Base stations can communicate with each other. They can easily located in a town/city because of the prominent size of their antenna above some buildings.
The Electromagnetic Waves
The form of energy transferred from one point to another at a speed of about 300,000 kilometers per second –the speed of light --, is called electromagnetic radiation. It is of several kinds. It can be visualized to spread like a wave. Therefore electromagnetic radiations are also called electromagnetic waves.
The distance between two adjacent crests of a wave is called its wavelength. The shorter the wavelength, the more energetic is the wave. Wavelength is also related to the frequency of a wave. Frequency is expressed in the units of Hertz, kilohertz (KHz) and megahertz (MHz). Other than wavelength, frequency and energy there is no difference between different kinds of electromagnetic radiations: radio waves, X-rays, microwaves and light. Radio waves are waves used for telecommunication
Electromagnetic waves in the radio frequency (RF) range can be divided into several ‘bands of frequencies’. Different bands that are allocated for different uses e.g. radio, television, aircraft communications, satellites, mobile phones and pagers. The band 0.5 – 1.7 megahertz (MHz) is allocated to conventional radio stations. Similarly the band 470 –750 MHz is allocated for TV transmission.
The bands of radio frequency allocated for use by cellular phone operators is 800 –900 MHz and 1800-1900 MHz.
A cell phone handset is also a low power radio transmitter/receiver. It can transmit as well as receive electromagnetic waves from its closest base station when it is powered on.
As soon as one turns on a cell phone handset it listens for SID (System Identification Code - a unique 5-digit number that is assigned to each carrier by the central authority say TRAI (Telecom Regulatory Authority of India) and is programmed into each handset when it is activated by a company.) on the control channel. The control channel is a special frequency that the phone and base station use to talk to one another about things like call set-up and channel changing. If the phone cannot find any control channels to listen to, it knows it is out of range and displays a "no service" message. The SID helps a cell phone company to identify cell phone handsets registered with it that are powered ON.
It also transmits a signal that includes the ESN to the base station of its parent company every few seconds. The computers attached to these transmitters/receivers maintain latest information about all the handsets distributed/registered by the parent company. This information at each base station is constantly updated. Thus base station of each cell knows the location of every powered on handset at any instance of time, through the codes SID and ESN.
When one dials a number on a handset signals are first converted into electricity and then into electromagnetic waves that are transmitted by it. The radio receiver of the cell in which handset is located at that time receives this signal. It is in then communicated to its computer to find the nature of the addressed party. If it is addressed to another cell phone serviced by the parent company, it finds out the location of the addressed handset and transmits signals to that base station, which in turn alerts the handset about the incoming call.
In case the call is addressed to a cell phone serviced by another company or to a landline telephone the cell directs the call into relevant network, which then directs the call in a similar fashion.
If a handset moves toward the edge of a cell, the cell's base station senses that the strength of the signals from that handset is diminishing. Meanwhile, the base station in the cell towards which it is moving (because is also listening and measuring signal strength on all frequencies) sees that the strength of radio waves from it is increasing. The two base stations coordinate with each other through the MTSO, and at some point, the handset gets a signal on a control channel telling it to change frequencies. Thus the handset is switched to the new cell.
If the handset moves to another city/state the SID on the control channel does not match the SID programmed into the handset. If the cellphone company provides roaming facility then the phone knows it is roaming. The MTSO of the cell that you are roaming in contacts the MTSO of the home system, which then checks its database to confirm that the SID of the phone you are using is valid. Your home system verifies your phone to the local MTSO, which then tracks your phone as you move through its cells. The amazing thing is that all of this happens within seconds!
Cell Phone Companies
Cell phone services are often offered by a number of companies . They are known as cell phone service providers. Each one of them has a network of its own to provide services in a limited region.
SID and ESN
All cell phones have special codes associated with them. There is a phone numbers allocated to each cell phone user. In India these numbers have 9 as their first digit. Then there are other code numbers that are used to identify the phone, the phone's owner and the service provider. SID (System Identification Code) is a unique 5-digit number that is assigned to each cell phone company by the government. When a cell phone is switched on, it listens for an SID on the control channel. The control channel is a special frequency that the phone and base station use to talk to one another. If the phone cannot find any control channels to listen to, it knows it is out of range and displays a "no service" message. When it receives the SID, the phone compares it to the SID programmed into the phone. If the SIDs match, the phone knows that the cell it is communicating with is part of its parent company..
Electronic Serial Number (ESN) is a unique 32-bit number programmed into the phone when it is manufactured.
Inside a handset
A cell phones handsets is somewhat like a palmtop computer. It is the most intricate device common people play with daily. But, if you were to take a cell phone apart, you will be surprised to discover very few parts inside it. They are:
A circuit board that has several chips (IC’s) on it.
An antenna
A liquid crystal display (LCD)
A keyboard (not unlike the one you find in a TV remote control)
A microphone
A speaker
A battery
Let us explore the function of each one of them. One chip on the circuit board translates the sound that is spoken near the microphone from analog to digital and the incoming digital signal back to sounds that can be heard through its speaker. Cell phones have such tiny speakers and microphones that it is incredible how well most of them reproduce sound. As you can see, the speaker is about the size of a 25p coin and the microphone is even smaller. The keyboard allows the user to enter information like the telephone number etc.
Digital or Analog: Electrical signals can be of two kinds, continuous or discrete. Electrical signals generated from sound by a microphone are of continuous kind. Such signals are known as analog signals. Signals that are used inside and between computers are made up of bursts of electrical current. They are known as digital signals.
Another chip on the circuit board, known as the microprocessor, handles all of the housekeeping chores for the keyboard and display. It deals with command and control signaling with the base station and also coordinates the rest of the functions on the board. Then there are some memory chips on the circuit board, which enable the cell phone to remember. A cell phone has to carry out many preprogrammed instructions. Therefore it has to remember all them. Memory is also essential for many other tasks a cell phone is useful for. The antenna is required to receive and transmit radio frequency (RF) signals. The rechargeable battery provides energy for all these functions.
History
The genesis of cellular phones can be traced back to 1947, when some engineers in USA looked at crude mobile (car) phones and realized that by using small cells (range of service area) with frequency reuse they could increase the traffic capacity of mobile phones substantially. However at that time, the technology to do so was nonexistent.
In USA, anything to do with broadcasting and sending a radio or television message out over the airwaves is decided by a department known as Federal Communications Commission (FCC). Since a cell phone is a type of two-way radio, in 1947, an American company AT&T proposed that the FCC allocate a large number of radio-spectrum frequencies so that widespread mobile telephone service would become feasible. But FCC declined this request.
The FCC reconsidered its position in 1968. AT&T and another well-known American company ‘Bell Labs’ then proposed the present form of cellular system. In this system many small, low-powered, broadcast towers, each covering a 'cell' a few miles in radius collectively cover a large area. Each tower uses only a few of the total frequencies allocated to the system. As the phones travel across the area, calls are passed from tower to tower.
Dr Martin Cooper, a general manager at an American company ‘Motorola’, is considered the inventor of the first modern portable handset. Cooper made the first call on a portable cell phone in April 1973. He made the call to his rival, Joel Engel. Thus Motorola was the first company to incorporate technology into portable device that was designed for use even outside of an automobile. By 1977, AT&T and Bell Labs had constructed a prototype cellular system.
Landline, GSM and CDMA
Conventional phones that are connected to one another largely through wires on the land are known as landline phones. Till very recently such phone service in India was provided only by government agencies like MTNL or BSNL. The technologies used for such telephones are rather ancient – more than fifty years old.
Cellular phones on the other hand had to overcome a major hurdle to become popular. Within a band of radio frequency, no two transmissions can use the frequency - at the same time. Therefore the number of people that can communicate using a band of frequencies is very limited. Cell phones therefore use technologies that have been developed in the last two decades only. GSM and CDMA are the names of two technologies that are most widely used by cellular companies in India. These are the technologies that enable a large number of people to communicate with one another using a very limited band of frequencies
GSM is an acronym for Global System for Mobile Telecommunications; cellular companies like AirTel, Hutch, Idea use this technology to provide their services. This technology is older then CDMA. In this technology mobile phones convert voices into a series of on-or-off electrical pulses, which are relayed in short bursts as packages of data. GSM is efficient because in the intervals between bursts, other phones can also send packets of data: in this way, this digital technology enables up to eight conversations to be held on the same channel virtually simultaneously.
CDMA is the acronym for the more recent technology called Code Division Multiple Access. CDMA takes an entirely different approach from GSM. Therefore handsets that are used for GSM services cannot be used for CDMA and vice versa. At present the major cellular companies in India that provide services using this technology are Reliance, Tata, and MTNL. In this technology, a spoken word or sentence from a user is first digitized, that is converted into electrical pulses like in GSM. But these pulses are coded and transmitted using the entire range of frequencies after ascribing them a particular code. At the receiving end they are combined together through the same code to generate the original word/sentence. This entire process occurs so fast that we cannot detect it.
The very many uses of Cell phone Handsets
A cell phone handset is useful not only for talking to people, it can be used for several other useful tasks too.
As a phonebook, diary, alarm timepiece
People often need to remember telephone numbers of their acquaintances, to use a telephone. Most cell phones today can store more than a hundred telephone numbers. The names can be displayed in alphabetical order on the screen. As soon as one clicks a button when a pointer on the screen points to a particular name, telephone number associated with it gets displayed on the screen and one can dial that number by just pressing another button. A cell phone handset also keeps record of recently dialed, received and missed calls, so that they can be dialed instantaneously.
One can use a cell phone as a personal diary also. A cell phone can be used to store information about dates important for its user or to keep information about future appointments. It can also alert its owner at a particular time on a particular day.
Send and receive text messages
Cell phones are useful not only for talking; one can also send short messages through them. These messages are called SMS (short messaging service). One can type in the text message with the same keys used for entering a phone number before dialing. Sending SMS is especially useful when you are not sure that the person to whom you want to convey the message may be immediately ready to receive it personally. An SMS message is stored in the handset and can be read anytime. This facility is becoming very popular because through it one can receive useful/interesting information almost anytime anywhere.
Voice Mail
The voice mail facility is very useful if one does not want to be disturbed by a telephone call but also does not want to miss any urgent message. In this facility the message is recorded and kept stored in the computers of the parent company. The user can access these messages whenever s/he wants to.
A camera or a sound-recorder
Certain handsets have a small camera built into them. With the help of this camera one can take pictures of a person or place around him and then instantly send it to some one who has a similar handset. Similarly some handsets have the facility to record sounds and play them at one’s own convenience.
Play games
A cell phone accompanies its owner almost everywhere, so manufactures of handsets have found an interesting application of the handset when one is getting bored. Cell phone handsets can be used to play some games when one is traveling or is alone. Such games can be downloaded from several vendors using the cell phone services. The games are especially interesting in the modern handsets that have a multicolor display.
As a calculator
Some cell phone handsets can also be used for small calculations useful for its owner in daily life. This is possible because the handset has a keyboard and a display screen just like a calculator.
Access Information on the Internet
Traditionally to access information one needs a computer and a telephone. A Cell phone handset has a microprocessor just like a computer and it is just like a telephone with a screen. It is therefore not very surprising that on certain handsets some cell phone companies are offering their clients the Internet services on their cell phone. An owner of such a handset can browse through the Internet almost like on a laptop computer.
Cell phone Etiquette
While using a conventional landline phone one is either at home or in a office, where are people around you are your relative or acquaintances. With a cell phone this is not always true. One may receive a telephone call anywhere and the alarm bell when one receives a call and the talk can disturbs people around. It is therefore necessary that people using cell phones should observe social etiquette. Here are a few do’s and don’t for cell phone users.
While riding public transport, one must try to avoid loud and eccentric conversations by keeping one’s voice low or to a relaxed, normal level. One must avoid extensive phone calls. There is a rule of thumb when talking on a cell phone and that is to maintain at least a 3 metre zone from anyone while talking.
One must keep ringer volume to a minimal. One can be less intrusive by using the silent or vibration options available on the handset. One can also set one’s cell phone to voice mail when it's inappropriate to take a call.
While attending public gatherings one must not interrupt by letting the sounds of one’s cell phone ringing. The sounds of a cell phone ringing are often very irritating for people around in a movie hall or a restaurant. One must avoid talking on cell phones while inside a theater, a library, a museum, or other enclosed community spaces, such as hospital emergency room.. If one has to make a call, one must make sure to take it to another area where the disruption to other people would be less.
One must always follow the rules about cell phone use in hospitals or on airplanes. These places have their own type of radio waves and outside interference such as a cell phone could interfere with the signals or other sensitive equipment. One must adhere to all posted signs and instructions in such places.
posted by charlie at 3:07 AM
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