Q3 The cell phone technology in toto is as under and if we have with us CB Radio more powerful than cell, ( not all cells have 3 watts; there is even cell with 0.6 watt). Always small fry are always blown as if they are a major life problem. Have you not seen in the web site where a few had written why cell phones should be spoken from the right side also; you tube is one source. "
The Cell Phone Technology It would be useful to give an overview of the cell phone technology here as this is quite inline with our installation. Let's see how a cell phone works? What makes it different from a regular phone? What do all those confusing terms like PCS, GSM <http://www.gsmworld.com/>, CDMA <http://www.cdmaonline.com/> and TDMA <http://www.iec.org/online/tutorials/tdma/index.html> mean? Let's start with the basics: In essence, a cell phone is a radio. One of the most interesting things about a cell phone is that it is actually a radio -- an extremely sophisticated radio, but a radio nonetheless. The telephone was invented by Alexander Graham <http://memory.loc.gov/ammem/bellhtml/bellhome.html> Bell in 1876, and wireless communication can trace its roots to the invention of the radio by Nikolai Tesla in the 1880s (formally presented in 1894 by a young Italian named Guglielmo Marconi <http://www.etedeschi.ndirect.co.uk/marconi/>). It was only natural that these two great technologies would eventually be combined! In the dark ages before cell phones, people who really needed mobile-communications ability installed *radio telephones* in their cars. In the radio-telephone system, there was one central antenna tower per city, and perhaps *25 channels* available on that tower. This *central antenna* meant that the phone in your car needed a powerful transmitter -- big enough to transmit 40 or 50 miles (about 70 km). It also meant that not many people could use radio telephones -- there just were not enough channels. The genius of the cellular system is the division of a city into small *cells*. This allows extensive *frequency reuse* across a city, so that millions of people can use cell phones simultaneously. In a typical analog cell-phone system in the United States, the cell-phone carrier receives about *800 frequencies* to use across the city. The carrier chops up the city into cells. Each cell is typically sized at about *10 square miles* (26 square kilometers). Cells are normally thought of as hexagons on a big *hexagonal grid*, like this: *Because cell phones and base stations use low-power transmitters, the same frequencies can be reused in non-adjacent cells. The two purple cells can reuse the same frequencies.* Each cell has a *base station* that consists of a tower and a small building containing the radio equipment (more on base stations later). A single cell in an analog system uses one-seventh of the available duplex voice channels. That is, each cell (of the seven on a hexagonal grid) is using one-seventh of the available channels so it has a unique set of frequencies and there are no collisions: - A cell-phone carrier typically gets *832 radio frequencies* to use in a city. - Each cell phone uses two frequencies per call -- a duplex channel -- so there are typically *395 voice channels* per carrier. (The other 42 frequencies are used for *control channels* -- more on this on the next page.) - Therefore, each cell has about *56 voice channels* available. In other words, in any cell, 56 people can be talking on their cell phone at one time. With digital transmission methods, the number of available channels increases. For example, a *TDMA-based* digital system can carry three times as many calls as an analog system, so each cell has about 168 channels available (see this page <http://electronics.howstuffworks.com/cell-phone6.htm> for lots more information on TDMA, CDMA, GSM and other digital cell-phone techniques). Cell phones have *low-power transmitters* in them. Many cell phones have two signal strengths: 0.6 watts and 3 watts (for comparison, most CB radios transmit at 4 watts). The base station is also transmitting at low power. Low-power transmitters have two advantages: - The *transmissions* of a base station and the phones within its cell do not make it very far outside that cell. Therefore, in the figure above, both of the purple cells can *reuse the same 56 frequencies*. The same frequencies can be reused extensively across the city. - The *power consumption* of the cell phone, which is normally battery-operated, is relatively low. Low power means small batteries <http://electronics.howstuffworks.com/battery.htm>, and this is what has made handheld cellular phones possible. The cellular approach requires a large number of base stations in a city of any size. A typical large city can have hundreds of towers <http://electronics.howstuffworks.com/cell-phone11.htm>. 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. Now let's analyses what happens we as you (and your cell phone) move from cell to cell. *From Cell to Cell *All cell phones have special *codes* associated with them. These codes are used to identify the phone, the phone's owner and the service provider. Let's say you have a cell phone, you turn it on and someone tries to call you. Here is what happens to the call: - When you first power up the phone, it listens for an *SID* (see sidebar) 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. - 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 *home* system. - Along with the SID, the phone also transmits a *registration request*, and the MTSO keeps track of your phone's location in a database -- this way, the MTSO knows which cell you are in when it wants to ring your phone. - The *MTSO* gets the call, and it tries to *find you*. It looks in its database to see which cell you are in. - The MTSO *picks a frequency pair* that your phone will use in that cell to take the call. - The MTSO communicates with your phone over the *control channel* to tell it which frequencies to use, and once your phone and the tower switch on those frequencies, the call is *connected*. You are talking by two-way radio to a friend! - As you move toward the edge of your cell, your cell's *base station* notes that your *signal strength* is diminishing. Meanwhile, the base station in the cell you are moving toward (which is listening and measuring signal strength on all frequencies, not just its own one-seventh) sees your phone's signal strength increasing. The two base stations coordinate with each other through the MTSO, and at some point, your phone gets a signal on a control channel telling it to change frequencies. This *hand off* switches your phone to the new cell. *As you travel, the signal is passed from cell to cell.* *Roaming* If the SID on the control channel does not match the SID programmed into your phone, then the phone knows it is *roaming*. The MTSO of the cell that you are roaming in contacts the MTSO of your 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. And the amazing thing is that all of this happens within seconds! *Cell Phones and CBs* A good way to understand the sophistication of a cell phone is to compare it to a CB radio or a walkie-talkie. - *Simplex vs. duplex* - Both walkie-talkies and CB radios are *simplex* devices. That is, two people communicating on a CB radio use the same frequency <http://electronics.howstuffworks.com/radio-spectrum.htm>, so only one person can talk at a time. A cell phone is a *duplex* device. That means that you use one frequency for talking and a second, separate frequency for listening. Both people on the call can talk at once. - *Channels* - A walkie-talkie typically has one channel, and a CB radio has 40 channels. A typical cell phone can communicate on 1,664 channels or more! - *Range* - A walkie-talkie can transmit about 1 mile (1.6 km) using a 0.25-watt transmitter. A CB radio, because it has much higher power, can transmit about 5 miles (8 km) using a 5-watt transmitter. Cell phones operate within *cells*, and they can switch cells as they move around. Cells give cell phones incredible range. Someone using a cell phone can drive hundreds of miles and maintain a conversation the entire time because of the cellular approach. *In simplex radio, both transmitters use the same frequency. Only one party can talk at a time.* *In duplex radio, the two transmitters use different frequencies, so both parties can talk at the same time. Cell phones are duplex.* In the next section, you'll get a good look inside a digital cell phone. *Inside a Cell Phone* On a "complexity per cubic inch" scale, cell phones are some of the most intricate devices people play with on a daily basis. Modern digital cell phones can process *millions of calculations per second* in order to compress and decompress the voice stream. *The parts of a cell phone* If you take a cell phone apart, you find that it contains just a few individual parts: - An amazing circuit board containing the brains of the phone - An antenna - A liquid crystal display <http://electronics.howstuffworks.com/lcd.htm> (LCD) - A keyboard (not unlike the one you find in a TV remote control <http://electronics.howstuffworks.com/inside-rc.htm>) - A microphone <http://electronics.howstuffworks.com/question309.htm> - A speaker <http://electronics.howstuffworks.com/speaker.htm> - A battery <http://electronics.howstuffworks.com/battery.htm> The circuit board is the heart of the system. Here is one from a typical Nokia <http://electronics.howstuffworks.com/framed.htm?parent=cell-phone.htm&url=http://www.nokia.com> digital phone: In the photos above, you see several computer chips. Let's talk about what some of the individual chips do. The *analog-to-digital* and *digital-to-analog* conversion chips translate the outgoing audio signal from analog to digital and the incoming signal from digital back to analog. You can learn more about A-to-D and D-to-A conversion and its importance to digital audio in How Compact Discs Work <http://electronics.howstuffworks.com/cd.htm>. The *digital signal processor* (DSP) is a highly customized processor designed to perform signal-manipulation calculations at high speed. *The microprocessor* The *microprocessor* <http://electronics.howstuffworks.com/microprocessor.htm> handles all of the housekeeping chores for the keyboard and display, deals with command and control signaling with the base station and also coordinates the rest of the functions on the board. The *ROM* <http://electronics.howstuffworks.com/rom.htm> and *Flash memory* <http://electronics.howstuffworks.com/flash-memory.htm> chips provide storage for the phone's operating system <http://electronics.howstuffworks.com/operating-system.htm> and customizable features, such as the phone directory. The *radio frequency* <http://electronics.howstuffworks.com/radio-spectrum.htm>* (RF) and power* section handles power management and recharging, and also deals with the hundreds of FM channels. Finally, the *RF amplifiers* handle signals traveling to and from the antenna. *The display and keypad contacts* The display <http://electronics.howstuffworks.com/lcd.htm> has grown considerably in size as the number of features in cell phones have increased. Most current phones offer built-in phone directories, calculators and even games. And many of the phones incorporate some type of PDA <http://electronics.howstuffworks.com/pda.htm> or *Web browser*. *The Flash memory card on the circuit board* *The Flash memory card removed* Some phones store certain information, such as the SID and MIN codes, in internal Flash memory, while others use external cards that are similar to SmartMedia <http://electronics.howstuffworks.com/flash-memory.htm> cards. *The cell-phone speaker, microphone and battery backup* Cell phones have such tiny speakers and microphones that it is incredible how well most of them reproduce sound. As you can see in the picture above, the speaker is about the size of a dime and the microphone is no larger than the watch battery beside it. Speaking of the watch battery, this is used by the cell phone's *internal clock chip*. What is amazing is that all of that functionality -- which only 30 years ago would have filled an entire floor of an office building -- now fits into a package that sits comfortably in the palm of your hand! *AMPS* In 1983, the analog cell-phone standard called *AMPS* (Advanced Mobile Phone System) was approved by the FCC and first used in Chicago. AMPS uses a range of frequencies <http://electronics.howstuffworks.com/radio-spectrum.htm> 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. Carriers A and B are each assigned *832 frequencies*: 790 for voice and 42 for data. A pair of frequencies (one for transmit and one for receive) is used to create one *channel*. The frequencies used in analog voice channels are typically *30 kHz* wide -- 30 kHz was chosen as the standard size because it gives you voice quality comparable to a wired telephone <http://electronics.howstuffworks.com/telephone.htm>. The transmit and receive frequencies of each voice channel are separated by *45 MHz* to keep them from interfering with each other. Each carrier has 395 voice channels, as well as 21 data channels to use for housekeeping activities like registration and paging. 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 do not offer many of the features common in digital cellular service, such as e-mail and Web browsing. *Along Comes Digital* *Digital* cell phones use the same radio technology as analog phones, but they use it in a different way. Analog systems do not fully utilize the signal between the phone and the cellular network -- analog signals cannot be compressed and manipulated as easily as a true digital signal. This is the reason why many cable <http://electronics.howstuffworks.com/cable-tv.htm> companies are switching to digital -- so they can fit *more channels within a given bandwidth*. It is amazing how much more efficient digital systems can be. Digital phones convert your voice into binary <http://electronics.howstuffworks.com/bytes.htm> information (1s and 0s) and then compress it (see How Analog-Digital Recording Works <http://electronics.howstuffworks.com/analog-digital.htm> for details on the conversion process). This *compression* allows between three and 10 digital cell-phone calls to occupy the space of a *single* analog call. 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! *Cellular Access Technologies* There are three common technologies used by cell-phone networks for transmitting information: - *Frequency division multiple access* (FDMA) - *Time division multiple access* (TDMA) - *Code division multiple access* (CDMA) Although these technologies sound very intimidating, you can get a good sense of how they work just by breaking down the title of each one. The first word tells you what the *access method* is. The second word, *division*, lets you know that it splits calls based on that access method. - FDMA puts each call on a separate *frequency*. - TDMA assigns each call a certain portion of *time* on a designated frequency. - CDMA gives a unique *code* to each call and spreads <http://electronics.howstuffworks.com/question326.htm> it over the available frequencies. The last part of each name is *multiple access*. This simply means that more than one user can utilize each cell. 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. *In FDMA, each phone uses a different frequency.* TDMA is the access method used by the Electronics Industry Alliance <http://electronics.howstuffworks.com/framed.htm?parent=cell-phone.htm&url=http://eia.org> and the Telecommunications Industry Association <http://electronics.howstuffworks.com/framed.htm?parent=cell-phone.htm&url=http://www.tiaonline.org/> 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*. Narrow band means "channels" in the traditional sense. Each conversation gets the radio for one-third of the time. This is possible because voice data that has been converted to digital information is compressed so that it takes up significantly less transmission space. Therefore, TDMA has *three times the capacity* of an analog system using the same number of channels. TDMA systems operate in either the *800-MHz* (IS-54) or *1900-MHz* (IS-136) frequency bands. *TDMA splits a frequency into time slots.* TDMA is also used as the access technology for Global System for Mobile communications (GSM). However, *GSM* implements TDMA in a somewhat different and incompatible way from IS-136. Think of GSM and IS-136 as two different operating systems <http://electronics.howstuffworks.com/operating-system.htm> that work on the same processor <http://electronics.howstuffworks.com/microprocessor.htm>, like Windows and Linux both working on an Intel Pentium III. GSM systems use *encryption* <http://electronics.howstuffworks.com/encryption.htm> to make phone calls more secure. GSM operates in the 900-MHz and 1800-MHz bands in Europe and Asia, and in the 1900-MHz (sometimes referred to as 1.9-GHz) band in the United States. It is used in digital cellular and *PCS-based* systems. GSM is also the basis for *Integrated Digital Enhanced Network* (IDEN), a popular system introduced by Motorola <http://electronics.howstuffworks.com/framed.htm?parent=cell-phone.htm&url=http://www.motorola.com> and used by Nextel <http://electronics.howstuffworks.com/framed.htm?parent=cell-phone.htm&url=http://www.nextel.com> . KR IRS 19922 On Mon, 19 Sept 2022 at 14:59, 'gopala krishnan' via iyer123 < [email protected]> wrote: > QUES ANSW MEDICAL 09-2022-01 > > Dear friends, > > These are information compiled as QA by me in 1998’s-2014’s and stored in > my computer. They are posted by *very learnt doctors in kidshealth.org > <http://kidshealth.org> etc. * > > *Many improvements have come in medical field. Hence some information may > have additions or some times changes.* > > *These are for general information, and for any health problem one has > to consult doctor.* > > *BEING COMPILATION THERE MAY BE ERRORS.* > > Sincerely, > > *R. Gopalakrishnan, 78, dated 19-09-2022* > > Q1 How many hours of sleep is good for an adult? > > > > A1 Adults who sleep eight hours or more may have *shorter life spans* than > those who sleep less, says a new research. > > > > Q2 Do Drinking coffee could help cure baldness? > > > > A2 Yes. Drinking coffee could help cure baldness as caffeine blocks > the effects of a chemical known to damage hair, say researchers. it > was found that caffeine had boosted the length of the hairs by > 33-40 percent. > > > > The scientists believe caffeine affects hair cells in such a way that > they are able to resist the damaging effects of dihydrotestosterone > (DHT), a chemical that contributes to baldness.* > > > > Most baldness is caused when hair follicles are exposed to too much DHT, > the researchers said. > > > > Q3 " When you try to call someone through mobile phone, don't put your > mobile > closer to your ears until the recipient answers”. What is the reason? > > > > A3 Because directly after dialling, the mobile phone would use it's maximum > signaling power, which is: > > > > 2watts = 33dbi Please Be Careful > > > > Please use left ear while using cell (mobile), because if you use the > right one it will affect brain directly. This is a true fact from Apollo > medical team. > > > > Q4 What is bad breath? > > > > A4 Bad breath is the common name for the medical condition known as > *halitosis* (say: ha-luh-*toe*-sus). There are many different things that > can cause halitosis – > > > > From not brushing your teeth to certain medical conditions. > > > > Poor oral *hygiene* leads to bad breath because when you leave food > particles in you mouth, these pieces of food can rot and start to smell > Plus, by not brushing your teeth regularly, plaque (a sticky, colorless > film) builds up on your teeth. > > > > Plaque is a great place for bacteria to live and yet another reason why > breath can turn foul > > > > And take care of your mouth by brushing your teeth at least twice a day > and flossing once a day. Brush/Clean your tongue , too, because bacteria > can grow there. > > > > Flossing once a day helps get rid of particles wedged between your teeth > gum disease, also known as *periodontal* (say: per-ee-o-*don*-tul) > *disease*, can cause bad breath and damage your teeth > > > > *For instance, if someone has uncontrolled diabetes , his or her breath > might smell like acetone (the same stuff that's in nail polish remover).* > > > > Sometimes sinus problems , and rarely liver or kidney problems, can cause > bad breath > > > > Q5 What are the changes during puberty? > > > > A5 During puberty, the body begins making hormones that spark > physical changes like faster muscle growth (particularly in boys) and > spurts in height and weight gain in both boys and girls* People who are > overweight as teens increase their risk of developing health problems, such > as diabetes and high blood pressure* Although BMI can be a good indicator > of a child's body fat, it doesn't always tell the full story. > > > > Someone can have a high BMI because he or she has a large frame or a lot > of muscle (like a bodybuilder or athlete) instead of excess fat. > > > > Getting Into Your Genes Heredity plays a role in body shape and what a > person weighs. People from different races, ethnic groups, and > nationalities tend to have different body fat distribution (meaning they > accumulate fat in different parts of their bodies) or body composition > (amounts of bone and muscle versus fat). But genes are not destiny. No > matter whose genes you inherit, you can have a healthy body and keep your > weight at a level that's normal for you by eating right and being active. > Genes aren't the only things that family members may share. It's also true > that unhealthy eating habits can be passed down, too Even simple forms of > exercise, such as walking, have huge benefits for a person's health > > > > Q6 What is pink eye? > > > > A6 It's called pinkeye because the white part of the eye and > inside the eyelids become red or pink when you have it. Conjunctivitis > lasts a short time, usually about a week or less, and then goes away by > itself or after treatment. Conjunctivitis is easy to catch just through > touching. You can get conjunctivitis by touching the hand of an infected > friend who has touched his or her eyes Kids also get conjunctivitis because > of allergies or because they get something irritating in their eyes, but > these kinds of conjunctivitis are not contagious Babies are usually given > the ointment and kids and adults get the eye drops. Unfortunately, these > drops won't work if a virus is causing your conjunctivitis > > > > Q7 What is the difference between the knee of a grown up and baby? > > > > A7 Babies are born without knee caps. They don’t appear until the child > reaches 2-6 years of age. > > Q8 according to mythology what do the reason given for a female child? > > A8 It is said that during an intercourse, excess of seminal fluid leads > to a boy child whereas excess of Ruj (female fluid of excitement) leads to > the birth of a girl child. > Q9 Do the diabetic show signs immediately on occurring? A9 NO. It is a > silent disease. Signs of the disease occur only after 10-12 years 40 > per cent of people have blood sugar abnormalities, known as glucose > intolerance, which can lead on to diabetes. Type II diabetes can damage > body organs, and is often "silent", not diagnosed. > > > > *My note- I was found diabetic when I went for a case of high fever and > body pain while working at Calicut in 1998 beginning on a blood test. * > > > > Q10 Do there will be an increase of BP for pregnant women? Do use of > contraceptives will increase BP? > > A10 For pregnant women,BP will be low upto 6 months. After 6 months, 15 > points increase, will be there.(Diastolic) Yes-Use of contraceptives will > increase BP. > > > > > > > > -- > You received this message because you are subscribed to the Google Groups > "iyer123" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/iyer123/1633310689.4116155.1663579778710%40mail.yahoo.com > <https://groups.google.com/d/msgid/iyer123/1633310689.4116155.1663579778710%40mail.yahoo.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "Thatha_Patty" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/thatha_patty/CAL5XZorDxw8joz2vPgZLrtp%3D-WBGLr3fJ610J9RBgkk4%2B5%2BHyg%40mail.gmail.com.
