A+ Guide to Managing and Maintaining Your PC Fifth Edition Chapter 17 Supporting Modems

2 A+ Guide to Managing and Maintaining Your PC, Fifth Edition You Will Learn… How modems work and how to install them About software that modems use to communicate with the OS Guidelines for troubleshooting modems

3 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Modems Devices used by PCs to communicate over phone lines Can be an external device connected to a USB or serial port Can be a modem card using either an ISA or PCI slot Can be a smaller and less expensive modem riser card

4 A+ Guide to Managing and Maintaining Your PC, Fifth Edition External Modem

5 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Modem Card

6 A+ Guide to Managing and Maintaining Your PC, Fifth Edition All About Modems Are both hardware and firmware MOdulation/DEModulation  Convert digital data to analog, then back to digital Provide an RJ-11 connection Can be half-duplex or full-duplex

7 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Modulation/Demodulation

8 A+ Guide to Managing and Maintaining Your PC, Fifth Edition RJ-11 Connection

9 A+ Guide to Managing and Maintaining Your PC, Fifth Edition How Modems Are Rated By how they set communication rules (handshaking) By how fast they pass data over phone lines (measured in bits per second or bps)

10 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Modem Speed 56 Kbps  Most commonly used modem speed rating today V.92 standard  Current standard for 56 Kbps transmission Maximum speed is often written into the manufacturer’s name for the modem

11 A+ Guide to Managing and Maintaining Your PC, Fifth Edition The Ceiling on Modem Speeds Analog phone lines were designed for transmission of human voice;  Affects ability to attain high transmission speeds for data Noise (line disturbance)

12 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Modem Standards Written by the CCITT, now called the ITU (International Telecommunication Union) The more standards a modem supports, the better it can communicate with a variety of other modems

13 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Modem Transmission Standards

14 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Modem Transmission Standards ( continued )

15 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Modem Transmission Standards ( continued )

16 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Data Compression Performed by firmware housed on the modem Follows one of three protocols (which also perform error correction)  MNP-5  CCITT V.42  V.42bis

17 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Error Correction Performed by firmware housed on the modem Breaks data up into small packets (frames)  Sending modem performs calculations on a frame, then sums calculations into a checksum, which is attached to the data frame  Receiving modem performs same calculations and runs a comparison of values before accepting Slows the process but guarantees almost 100% accuracy

18 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Key Points about Handshaking Answering modem sends a guard tone so connection is not broken Answering modem establishes a carrier Equalization stage; modem speed (line speed) is set between modems Modem speakers turn off; methods of data transmission are agreed on

19 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Serial Port (UART) Settings UART chip is responsible for communications over a serial port  External modem is likely to use a serial port  Internal modem has serial port (UART) logic on the modem card and must be assigned its own COM port that its UART controls Port settings control serial-port communication

20 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Port Settings

21 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Port Settings ( continued )

22 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Port and Modem Settings Communication between DTE and DCE (computer and modem) is controlled by port settings  RS-232  Digital  Port speed

23 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Port and Modem Settings ( continued ) Communication between two DCE devices (two modems) is controlled by modem settings  Phone line  Analog  Line speed

24 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Port and Modem Settings ( continued )

25 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Modem Features Caller ID Call waiting Display readout Fax capabilities Flash ROM Plug and Play for Windows Voice/data capability Auto-answer Expansion slot or port type

26 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Installing an Internal Modem Read documentation Determine available serial port Set jumpers or DIP switches on modem card Turn off computer; remove case; mount card Replace cover Plug phone line from house into line jack on modem

27 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Setting Jumpers on an Internal Modem

28 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Installing an External Modem Connect high-quality cable to modem and to serial or USB port Plug electrical cord from modem into an 110V AC outlet Plug phone line from house into line jack on modem

29 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Configuring a Modem Using Windows XP Windows Plug and Play will detect new hardware device Verify the OS configured the modem correctly Verify that modem speed is set to highest value in Maximum Port Speed text box To use Windows to make calls without using other software, create a dial-up Networking Connection

30 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Creating a Windows XP Dial-up Network Connection

31 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Configuring a Modem Using Windows 98 Easier to use manufacturer’s drivers on CD When verifying modem properties:  Set modem speed at highest value in drop-down list  Set port protocol at “8, No, and 1” (represents 8 bits, no parity, 1 stop bit)  Use hardware flow control

32 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Creating a Windows 98 Dial-up Network Connection

33 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Ways to Test a Modem Use the HyperTerminal utility Use the OS to perform a diagnostic test  AT commands

34 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Testing a Modem with AT Commands

35 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Troubleshooting Guidelines for Modems What works and what doesn’t work? What worked in the past but does not work now? What has changed since things last worked? Ask questions of users Try simple things first

36 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Potential Modem Problems Modem does not respond Modem says there is no dial tone, but you can hear it Modem dials, then says the other end is busy, even when you know it is not Sending modem and receiving modem take a long time to negotiate the connection

37 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Potential Modem Problems ( continued ) During a connection, it sounds as if handshaking starts all over again File transfers are slow Modem loses connection at odd times or is slow Modem drops the connection and gives NO CARRIER message

38 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Potential Modem Problems ( continued ) When weather is bad, connection often disconnects When large files are downloaded, some data is lost Connection fails when large files are uploaded or downloaded Nothing but garbage across the connection

39 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Troubleshooting Modems

40 A+ Guide to Managing and Maintaining Your PC, Fifth Edition Summary How modems work Installing and troubleshooting modems