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Modem

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  • 1. Seminar on MODEMS
  • 2. MODEMS Converts analog signals to digital and vice-versa
  • 3. MODEMS
    • A modem is a device or program that enables
    • computer to transmitt data over telephone lines.
    • Computer information is stored digitally, whereas
    • information transmitted over telephone lines is
    • transmitted in the form of analog waves.A modem converts between these two forms.
  • 4. Introduction
    • Modulator – converts digital information to analog
    • Demodulator – converts analog information to digital
  • 5. Basic Principle 0101
  • 6.  
  • 7. Basic Structure
  • 8. How Modulation is used for data transfer ? 10100101011001010 - the transmitted symbol sequence will be: 6 4 5 1 2.
  • 9. Classification of Modems
    • Range
    • Line Type
    • Operation Mode
    • Synchronization
    • Modulation
    • Data Rate
  • 10. Range Line Type
    • Short Haul
    • Voice Grade
    • Wide Band
    • Dial-up
    • Leased
    • Private
  • 11. Operation Mode Modulation
    • Simplex
    • Half-Duplex
    • Full-Duplex
    • AM
    • FM
    • PM
    • TCM
  • 12. CABLE MODEM
    • Cable Modems make access to TV cable, and let you get  high-speed internet access.
    • Availability is still limited in many areas, but is growing rapidly.
  • 13. EXTERNAL MODEM
    • It usually plug in through a serial port, or  a USB port. 
    • External modems cost the most, but have the benefits of being easily installed.
    • Also plugs into telephone line.
    • External power supply is needed.
    • Holder case is required.
    • Often they have the  indicators that tell the status of your connection there is one standard interface for connecting external modems to computers called RS-232.
  • 14. TYPICAL INDICATERS ON EXTERNAL MODEMS FRONT PANAL
    • HS = HIGH SPEED
    • AA = AUTO ANSWER
    • CD =CARRIER DETECT
    • OH =OFF HOOK
    • RD =RECIVED DATA
    • SD =SEND DATA
    • TR =TERMINAL READY
    • MR = MODEM READY
  • 15. INTERNAL MODEM
    • It can insert into a vacant expansion slot.
    • No external power supply is needed.
    • No holder case is required.
    • Least expensive at given speed.
    • Incompatible with different kind of PCs.
    • These modems go inside the computer, and usually plug directly into the motherboard.
  • 16. ISDN MODEM
    • ISDN is an abbreviation for Integrated Services Digital Network.
    • There is no such thing as a noisy or fuzzy line. 
    • always runs at 64kbps.
    • Ability to bond multiple "B" channels to get speeds of 128kbps.
    • Call Setup is very fast (dialing, handshake and authentication), usually under 2 seconds (compared with 15 seconds at least for most analog modems).
    • Ability to get 2 calls at the same phone number (one line is for voice, and the other line for your internet connection).
  • 17. WIRELESS MODEM
    • Convert digital data into  radio signals and back. 
    • Support a maximum data transmission rate of 19.2Kbps (kilobits per second).
    • Wireless modems can be used up to 20-30 miles (30-50 KM).
    • Operation is in the 900 MHz and 2.4 GHz. 
    • Modem names include –
    • BreeseLINK, LATNET-Radio Data Links, AirLink Wireless Modems, and Open Minds.
  • 18. FAX MODEM
    • A fax modem in PC can send data to a standard fax machine, which converts data into hard copy form.
    • On the other hand a PC fax system can receive a transmission from a standard fax machine and capture the image into graphic file.
    • The fax server eliminates the need for each PC in the network to be equipped with its own fax modem and telephone line.
  • 19. DSL MODEM
    • DSL Modems: DSL (Digital Subscriber Line)  service is usually offered through  the phone the company/ISP.
    • You can leave your Internet connection open and still use the phone line for voice calls.
    • The speed is much higher than a regular modem (up to 1.5 Mbps )
    • DSL doesn't necessarily require new wiring; it can use the phone line you already have
  • 20. 56K MODEMS
    • The latest modems are equipped with many facilities they have a speed which can even reach a data transfer speed of 56.6 kbps . They have all facilities like fax, auto-answering, auto-dialing etc.
    • They are asymmetrical in that the downloading
    • is a maximum of 56kbps.
    • The uploading can be maximum of 33.6 kbps.
  • 21. Modem Speed
    • The Modulation Speed
    • The Serial Port Speed
  • 22. SPEED OF MODEM
    • Modem speed is rated in bps (bits per second).  So a 56k modem transmits at 56,000 bits per second in theory. While 8 bits make a byte, and 1024 bits equal one kilobits, a 56k modem will transmit a maximum of approximately 7 kilobytes of information every second.   A modem will never connect higher than what it is rated for.
  • 23. Modem Installation
    • Modem Cable Selection
    • Selection of Port
  • 24. STANDARDS
    • ITU :-- International Telecommunication. Union.
    • ISO :-- International Standard Organization.
    • CCITT :-- International Consultative Committee For Telephone And Telegraphy.
  • 25. DIFFERENT CCITT STANDARDS
  • 26.
    • Bell 103 & 212A :
    • Bell 103 transmits at 300 bps at 1 bit per baud. Bell 212A was the next step up, capable of two bits per baud. It was capable of 1200bps at 600 baud.
    • V.21:
    • It was a sort of international standard. It is not compatible with Bell protocols, and is only capable of 300bps.
  • 27.
    • V.22 :
    • Shares the features of V.21, but was capable of
    • 1200bps ,ran at 4 bits per baud for a total of 2400bps
    • V.23:
    • This allowed the modem to send and receive data at the same time, although it could send data only at 75bps. This standard was developed to lower the cost of modems. A 1200 bps modem was very expensive at the time.
    • V.29 :
    • A half-duplex standard, meaning one-way. It works at 9600bps. The standard is not laid out well for modems, therefore isn't much used. The protocol is most often used for fax machines
  • 28.
    • V.32 :
    • It was a full-duplex standard and operated at 9600bps, with a 2400 baud rate.
    • V.32bis :
    • It transmitted 6 bits per baud, allowing throughputs of 14,400 bps.
    • V.32 Fast:
    • Better known as the 28,800 bps modem.
    • V.34 :
    • The latest real modem standard. It provides a reliable 28,800 bps connection. the standard is often used for 33,600 bps transmissions.
  • 29.
    • Error Correction :
    • Error Correction is an important feature in the fastest modems. It allows fast reliable connections over standard phone lines, even past noise.
    • Modems use the V.42 error correction protocol. With it, the modem can detect damaged data streams, and the data will be resent.
    • The V.42bis protocol is just like V.42, but incorporates data compression. A 14.4 modem, with data compression, can boast transmission rates of 57,600 bps.
  • 30. PROTOCOLS
    • V.34 -  for 28.8k and 33.6k communications. 
    • K56Flex - for 56k communication,  created by Lucent and Rockwell. 
    • X2 - for 56k communication,  created by US Robotics (3com). 
    • V.90 - This is the International Standard for 56k modems.  
    • V.92 - This is an  ITU (international Telecommunication Union) standard for 56K modems, but three new features have been added -- faster connections (on 50%), better uploading, and data and voice support:
  • 31. ERROR CORRECTION PROTOCOL
    • There are 2 protocols that are used to correct errors on a connection:
    • V.42 (LAPM) – This is the International Standard for doing Error Correction .
    • MNP –  an old protocol that most modems support. 
  • 32. Today’s Status & Future Trends
    • Semiconductor modems introduced
    • Increased speed
    • Less complication
    • More use due to internet
    • Frequent use of internal modem
  • 33. LATEST TRENDS OF MODEMS
    • They have a speed which can even reach a data transfer speed of 56.6 kbps .
    • They have all facilities like fax, auto-answering, auto-dialing etc.
    • The latest facility available in modems is caller id, Distinctive ring detection, Faxing. etc.
  • 34. Bibliography
    • Hardware Bible Winn.L.Rosch
    • Data Communications Prakash .C. Gupta
    • Data Comm. & Networking Behrouz .A. Forouzan
    • Internet