1.What is base station?
Base station is nothing but which interconnects two or more telephone systems.
2.What is multiplexing?
multiplexing is the process of sending two or more signals through a single communication channel.
There are two types of multiplexing:
* Frequency domain multiplexing.
* Time domain multiplexing.
3.Difference between CDMA & GSM?
The basic difference lies in the Multiplexing method used in the aerial communication i.e. from Mobile Tower to your mobile and vice versa.
CDMA uses Code Division Multiple Access as
the name itself indicates, for example you are in a hall occupied with number of
people speaking different language. You will find that the one language you know
will be heard by you and the others will be treated like noise. In the same
manner each CDMA mobile communication takes place with a "code" communicating
between them and the other end if one is knowing that code then only it can listen to the data being transmitted i.e. the
communication is in the coded form.
On the other hand GSM (Global System for Mobile Communications) uses narrowband TDMA, which allows eight simultaneous calls on the same radio frequency. TDMA works by dividing a radio frequency into time slots and then allocating slots to multiple calls. In this way, a single frequency can support multiple, simultaneous data channel.
On the other hand GSM (Global System for Mobile Communications) uses narrowband TDMA, which allows eight simultaneous calls on the same radio frequency. TDMA works by dividing a radio frequency into time slots and then allocating slots to multiple calls. In this way, a single frequency can support multiple, simultaneous data channel.
GSM provide international roaming while CDMA does not.
GSM works on 900 and 1800 MHz while CDMA
does only on 900 MHz.
4. What is Barkhausen criteria?
Barkhausen criteria, without which
you will not know which conditions, are to be satisfied for oscillations.
Oscillations will not be sustained if, at the oscillator
frequency, the magnitude of the product of the transfer gain of the amplifier
and the magnitude of the feedback factor of the feedback network ( the magnitude
of the loop gain ) are less than unity?.
The condition of unity loop gain -Aβ = 1 is called the Barkhausen criterion. This condition implies that
Aβ
= 1and that the phase of - Aβ is zero.
The condition of unity loop gain -Aβ = 1 is called the Barkhausen criterion. This condition implies that
Aβ
= 1and that the phase of - Aβ is zero.
Barkhausen Criteria: For sustained oscillations
1. The total phase shift around a loop is precisely 0 degree or 360 degree.
2. The magnitude of the product of open loop gain of the amplifier and the magnitude of the feedback factor is unity.
That is │Aβ│=1
1. The total phase shift around a loop is precisely 0 degree or 360 degree.
2. The magnitude of the product of open loop gain of the amplifier and the magnitude of the feedback factor is unity.
That is │Aβ│=1
5.How many satellites are
required to cover the earth?
3 satellites are required to cover the
entire earth, which is placed at 120 degree to each other. The life span of the
satellite is about 15 years.
6.What is a transducer and transponder?
A transducer is a device, usually electrical, electronic, electro-mechanical, electromagnetic, photonic, or photovoltaic that converts one type of energy or physical attribute to another for various purposes including measurement or information transfer.
6.What is a transducer and transponder?
A transducer is a device, usually electrical, electronic, electro-mechanical, electromagnetic, photonic, or photovoltaic that converts one type of energy or physical attribute to another for various purposes including measurement or information transfer.
In telecommunication, the term transponder (short-for
Transmitter-responder and sometimes abbreviated to XPDR, XPNDR, TPDR or TP) has
the following meanings:
* An automatic device that receives, amplifies, and retransmits a signal on a different frequency (see also broadcast translator).
* An automatic device that transmits a predetermined message in response to a predefined received signal.
* A receiver-transmitter that will generate a reply signal upon proper electronic interrogation.
A communications satellite?s channels are called transponders, because each is a separate transceiver or repeater.
* An automatic device that receives, amplifies, and retransmits a signal on a different frequency (see also broadcast translator).
* An automatic device that transmits a predetermined message in response to a predefined received signal.
* A receiver-transmitter that will generate a reply signal upon proper electronic interrogation.
A communications satellite?s channels are called transponders, because each is a separate transceiver or repeater.
Transducer is a device which converts any
physical quantity such as temperature,pressure etc into equivalent electric
signal.
transponder (short-for Transmitter-responder)is an automatic device that receives, amplifies, and retransmits a signal on a different frequency.example communication,broadcasting satellites.
transponder (short-for Transmitter-responder)is an automatic device that receives, amplifies, and retransmits a signal on a different frequency.example communication,broadcasting satellites.
7. What is
crosstalk?
Crosstalk is a form of interference caused by signals in nearby conductors. The most common example is hearing an unwanted conversation on the telephone. Crosstalk can also occur in radios, televisions, networking equipment, and even electric guitars.
8.Explain Full duplex and half duplex.
Full duplex refers to the transmission of data in two directions simultaneously. For example, a telephone is a full-duplex device because both parties can talk at once. In contrast, a walkie-talkie is a half-duplex device because only one party can transmit at a time.
Most modems have a switch that lets you
choose between full-duplex and half-duplex modes. The choice depends on which
communications program you are running.
In full-duplex mode, data you transmit does not appear on your screen until it has been received and sent back by the other party. This enables you to validate that the data has been accurately transmitted. If your display screen shows two of each character, it probably means that your modem is set to half-duplex mode when it should be in full-duplex mode.
In full-duplex mode, data you transmit does not appear on your screen until it has been received and sent back by the other party. This enables you to validate that the data has been accurately transmitted. If your display screen shows two of each character, it probably means that your modem is set to half-duplex mode when it should be in full-duplex mode.
full duplex is nothing but device which
allows us to transmite and recieve sinultenously with greater efficiency.
.
9. Difference between mobile and a
cell phone.
There is no difference, just language use,
which differs from country to country, so in Britain it is called a mobile, and
in USA and South Africa and other places a
cell phone. Even in Europe the name differs. The Germans call it a "handy",
which in English has completely another meaning as an adjective, meaning useful.
In Italy it is called a telofonino or "little
phone". This difference in British and American English is also evident
in many other things we use every day, like lifts
and elevators, nappies and diapers,
pickups and trucks. The list goes on and on,
any student of English has to decide which he or she will use, as the default
setting.
mobile is a technology and cell phone is sub
technology in it. to understand it clearly consider a walkie talkie and cell
phone. Both are different technologies but both are mobile. The way they
communicate is also different.
10. Difference between electronic and
electrical.
Electronics work on DC and with a voltage
range of -48vDC to +48vDC. If the electronic device is plugged into a standard
wall outlet, there will be a transformer inside which will convert the AC
voltage you are supplying to the required DC
voltage needed by the device. Examples: Computer, radio, T.V,
etc...
Electric devices use line voltage (120vAC, 240vAC, etc...). Electric devices can also be designed to operate on DC sources, but will be at DC voltages above 48v. Examples: are incandescent lights, heaters, fridge, stove, etc...
Electric devices use line voltage (120vAC, 240vAC, etc...). Electric devices can also be designed to operate on DC sources, but will be at DC voltages above 48v. Examples: are incandescent lights, heaters, fridge, stove, etc...
No comments:
Post a Comment