Connecting on the Road


Once you have the necessary hardware and software, you will find that there are many different ways to connect to the Internet, or any other computing system for that matter. In this section we address the actual process of making those connections.

As mentioned before, there are two general ways to connect: wired and wireless. Wired connections are generally faster and more reliableat least so far.

Hotel High-Speed Connections

The fastest wired connection you can make with your laptop is via its network interface to an accommodating LAN that has high-speed Internet access. These LANs can be found in branch offices of your company, in airline premium clubs, and in some forward-thinking coffee shops . The most likely place, however, for a business traveler to find high-speed wired access is in a hotel room. A Web site www.wiredhotels.com keeps a database of hotels with high-speed access, with a short description of the services available. Currently this site has listings for over 3,000 hotels.

When reserving a room, be sure to check if a room with fast Internet access is available. When you arrive in the room, check that the access works. If it is not there or does not work correctly, ask the front desk to switch you to another room that is better equipped.

DHCPAny Address Will Do

Before you can become part of a hotel LAN or any other LAN that supports the popular TCP/IP protocol, you will need to be sure that the LAN adapter in your laptop is configured with the right address. Specifically, this is called an IP (Internet Protocol) address and consists of four numbers , from 0 to 255, separated by periods. Web surfers are well acquainted with such addresses.

The requirement of having the right IP address provides a modest layer of security in corporate LANs, but it also proves to be a pain in the neck for corporate IT staffers and an unnecessary pain for low-security LANs such as those in hotels. To solve this problem, the DHCP (Dynamic Host Configuration Protocol) server was developed. This program automatically doles out correct IP addresses to any new computers that happen to show up on a LAN.

How to Accept an IP Address Automatically

Most notebook computers are, by default, set up as DHCP clients that is, as network members that automatically accept whatever IP address the DHCP server doles out to them. If, however, your notebook has been set up with a specific IP address for use with a corporate LAN, you will need to temporarily reconfigure it. Here's how:

  1. Access the Control Panel in Windows. (In Windows XP, click Start, Control Panel. In other Windows versions, click Start, Settings, Control Panel.)

  2. Double-click the Network or Network Connections icon (in Windows XP be sure to select Classic View from the list on the left side of the screen).

  3. Right-click the icon referring to the network adapter in your laptop, usually identified as "Local Area Connection," and select Properties from the list that appears.

  4. Select Internet Protocol (TCP/IP) from the list of items and click the Properties button.

  5. If a specific IP address and subnet mask are listed (see Figure 12.7), write these down and store them in a safe place. You will need these to restore the configuration later.

    Figure 12.7. The Internet Protocol (TCP/IP) properties for a LAN connection under Windows XP.

    graphics/12fig07.gif

  6. Check the box labeled Obtain an IP Address Automatically if it is not already checked.

  7. Click OK.

Note that when you return to the office you will have to revert to the original configuration. In this case, you will have to choose Use This IP Address instead of Obtain an IP Address Automatically and then enter the IP address and subnet you recorded earlier.

STSN

A company called STSN (www.stsn.com) specializes in providing high-speed access to hotels. Hotels affiliated with STSN have what STSN calls a "smart box" in every guestroom (see Figure 12.8). Users simply plug in with either an Ethernet or USB cable and power up their laptops. Then all they should need to do is launch their Internet browser. Once connected, the user can take advantage of the hotel's T1 or DSL high-speed Internet connection. (If the laptop does not have a LAN adapter, the user can connect the laptop's modem to a phone jack on the smart box.) STSN reports that it provides firewalls for each room and that users can print documents that can later be retrieved at the hotel's front desk.

Figure 12.8. The connection module used by STSN to provide high-speed access in hotels.

graphics/12fig08.jpg

In return for high-speed access, these hotels usually charge a flat fee for access during each 24- hour period (noon to noon). The charge is typically $9.95. Weekly rates are also available.

Using Wireless Hotspots

Most wireless communication by laptops occurs via wireless LANs. These WLANs now offer much of the same speed as wired LANs while bestowing laptops with a modest degree of mobility. The best thing about WLANs is that they continually get better. More and more WLANs are being installed, for less and less money, while speeds continue to increase.

Usually these WLANs are private, meant only for the staff of a particular office or the residents of a certain house. A number of establishments, however, have begun to offer public WLANs, which are called hotspots . A laptop user can stay in good contact with the Internet by traveling from one hotspot to another, much as a frog jumps from one lily pad to another.

Finding Hotspots

Although the number of hotspots is growing, finding one can sometimes be a hit-and- miss proposition. A few Web sites have stepped in to provide directories of hotspots. Here is a brief sampling of the more popular sites:

  • www.80211hotspots.com

  • www.hotspot-locations.com

  • www.intel.com/support/notebook/hotspots/provider.htm

  • www.wifinder.com

New hotspots are appearing on an almost daily basis. Because of this, it is difficult for any Web directory to keep up with the many changes. The Intel site in the preceding list seems to offer the most comprehensive list of sites.

Most hotspots are commercial businesses that charge either by the hour, day, or month. Some commercial hotspots are offered as a free service in exchange for other patronage . For example, as we went to press, certain MacDonald's locations were offering one free hour of Internet access to all customers who ordered a certain amount of food. A number of companies have set up networks of hotspots throughout the country. Signing up with one of these companies enables you to access any of its hotspots throughout the country. So far, however, none of these wireless Internet service providers (or WISPs) have achieved a dominant position, which means that travelers may have to establish accounts at more than one WISP. Intel keeps an extensive list of WISPs on its Web site (www.intel.com/support/notebook/hotspots/provider.htm). Here is a short list of the larger WISPs:

  • www.boingo.com

  • www.cafe.com

  • www.hotspotzz.com

  • www.peekaboo-wireless.com

  • www.stayonline.net

  • www.surfandsip.com

  • www.tmobile.com

  • www.wayport.com

The Boingo site also includes some information about free hotspots. T-Mobile provides the wireless LAN access at most Starbucks coffee shops. The T-Mobile site provides information on the location of those coffee shops.

Finding Free Hotspots

One of the nicest things about wireless LANs is that some of them are free. A few of these sites offer this service in the hopes that users will reimburse the provider in other ways (for example, by buying more coffee). But often the service is provided completely altruistically without any ulterior motives. The trick is to find these sites.

A few sites offer directories of free sites. On its site, Boingo lists its own commercial sites along with some free sites. Some sites, such as the following, specialize in providing information on free sites:

  • www.wififreespot.com

  • www.nycwireless.net

Free sites come and go much faster than any directory can keep up. For that reason, some users try to find their own free sites. Using sniffer software, a laptop will spot and identify any wireless LAN with range. As I write this, a version of sniffer software is available on Boingo's Web site. This software identifies any WLAN within range, noting its service set identification (SSID) code, the type of access point used, and, if not protected, the identification number or MAC of the access point. The software also indicates whether the WLAN is encryption protected. If the site is not protected by encryption and has a generic or welcoming SSID (such as "FREEACCESS"), some users consider it a free site and take advantage of the high-speed access that is seemingly offered.

The process of driving around a neighborhood searching for available WLANs is called war driving . Although technically feasible and in many cases quite easy, the act of connecting to someone's WLAN without permission is discourteous and could be illegal. When you set up your own WLAN, be aware of how easily accessible it can be, and be sure to institute proper security measures. A Web site called www.wifimaps.com publishes maps of wireless LANs, many of which appear to have been identified by war driving (see Figure 12.9). The small triangles indicate the presence of a WLAN. In many cases, the SSID of the WLAN is listed. This map covers a few blocks in downtown New York City. The map indicates how easy it is to locate and identify WLANs.

Figure 12.9. A sample map of wireless LANs taken from the Web site www.wifimaps.com. (Figure from www.wifimaps.com.)

graphics/12fig09.jpg

How to Connect to a Hotspot

To connect to a hotspot, the first thing to do is to determine if you are within range of a hotspot access point. Most WLAN PC Cards are bundled with a utility program that indicates how strong the wireless LAN signal is. Usually this is indicated by a green icon of some type.

Once you know you are in range of an access point, you need to be sure your laptop is set to the right IP address. Unless you know otherwise , most WLANs require your laptop to accept an IP address automatically. To set your laptop in this configuration, see the section earlier in this chapter titled "How to Accept an IP Address Automatically."

Finally, you will need to set the correct service set identification (SSID) code on your laptop's WLAN PC Card adapter. The exact instructions for this may vary from one adapter to another. Follow the manufacturer's directions for accessing the "Configuration" or "Properties" dialog box for your WLAN adapter. Note that some manufacturers refer to the SSID as the ESSID.

Cellular Modems

If you are beyond the range of a wireless LAN and yet still want to establish a wireless connection, one of the easiest and least expensive ways is via a cellular connection. Most business people today carry a portable cell phone, and most new cell phones are capable of functioning as a cellular modem with the addition of a relatively inexpensive adapter cable. Note that, as mentioned previously in this chapter, cellular data connections can be irritatingly slow.

To make a cellular data connection, you must be sure that you are getting a good cellular signal. The best and easiest way to determine this is to look at the signal strength indicator on your cell phone.

Once you are sure of a good cellular signal, the next step is to connect the phone to the laptop. Most older cables connect to the serial port, which is disappearing from some of the latest notebook computers. The newer cables attach to USB connectors, which are faster and easier to use.

The next step depends on the particular cell phone you are using. In some cases, the cell phone appears to the laptop's Windows operating system as an ordinary wired modem. In other cases, you need to install a special driver program from the CD-ROM that came with the cell phone's data-connection adapter cable.

Note that many cell phones enable you to connect in one of two ways: either via a circuit-switched connection or in packet-switched mode. The mode you choose depends on the amount of data you intend to access, the probable duration of your connection, and the way your cellular phone company charges. If you download large amounts of data only once per day and your cellular company has a very low per-minute charge for voice calls, you should use the circuit-switched technique. Otherwise, use packet-switched mode, which is sometimes referred to as an "always-on" connection. A circuit-switched connection works just like a traditional dial-up modem connection. A packet-switched connection works like a DSL or cable modem connection.

Because cellular data connections are very slow (often only 14.4Kbps), use them only for applications such as email that do not require significant bandwidth. Postpone your large downloads until you can make a broadband connection.

Wired Modem Connections

Out on the road, you cannot depend on finding a high-speed connection or a decent wireless LAN signal. In many areas, even cellular connections may be spotty. Therefore, it is always prudent to have your trusty old wired modem ready as a backup connection. It may be slower than what you are used to, but it usually works.

What to Bring

The additional hardware needed for a modem connection is not heavy at all. The most important tool is a modular phone line, at least 6 feet in length. Because some hotels and offices use a digital PBX phone system, it is usually a good idea to bring a line tester as well. This keeps your modem from being fried by the high ringing voltages that these phone systems use. If it is important for you to be in touch, you might also bring along a second modem in a lightweight PC Card format.

How to Connect with a Modem

In most hotel rooms in the United States, connecting with a modem is now fairly straightforward. These rooms usually are equipped with phones that feature a phone jack designed for laptop connections.

Caution

In an effort to increase revenue, some hotels now gouge their customers with exorbitant phone rates, even for local calls. To avoid an unpleasant surprise at the checkout desk, examine the hotel's phone rates before you connect to the Internet.


Modem InstructionsThe AT Command Set

Most of the time, when you use a modem you never have to interact with it directly. Your communications software usually handles that. There are occasions, however, when you need to access and control the modem directly. This happens, for example, when something is not working and you need to troubleshoot the system.

Modems respond to a series of commands, most of which are prefaced with the letters AT (for attention ). Because of this, these commands are usually called AT commands.

The AT command set dates back to the original personal computer modems introduced by D.C. Hayes & Associates in 1978. Most current modem manufacturers incorporate the original Hayes set of commands and enhance these with special commands that can take advantage of any special features incorporated in new modems. Table 12.2 lists the commands from a typical PC Card modem: 3Com's 3CXM556 56K cellular modem PC Card with an XJACK connector. Many of these commands, particularly the general commands, apply to all modems.

Table 12.2. A Sample AT Command Set

General Modem Commands

&$

HELP, Ampersand Commands

 

n=1 Speaker ON Until CD

A/

Repeat Last Command

 

n=2 Speaker Always ON

A>

Continuously Repeat Command

 

n=3 Speaker OFF During Dial

AT

Command Mode Prefix

On

n=0 Return Online

A

Answer Call

 

n=1 Return Online & Retrain

Bn

n=0 V32 Mode/CCITT Answer Seq

P

Pulse Dial

 

n=1 Bell Answer Seq

Qn

n=0 Result Codes Sent

Dn

Dial a Telephone Number

 

n=1 Quiet (No Result Codes)

 

n=0..9#*TPR,;W@!()-

 

n=2 Verbose/Quiet ON Answer

DL

Dial Last Phone Number

Sr=n

Sets Register "r" to "n"

DSn

Dial Stored Phone Number

Sr?

Query Register "r"

D$

HELP, Dial Commands

S$

HELP, S Registers

En

n=0 No Command Echo

T

Tone Dial

 

n=1 Echo Command Chars

Vn

n=0 Numeric Responses

Fn

n=0 Online Echo

 

n=1 Verbal Responses

 

n=1 No Online Echo

Xn

n=0 Basic Result Codes

Hn

n=0 ON Hook (Hang Up)

 

n=1 Extended Result Codes

 

n=1 OFF Hook

 

n=2-4 Advanced Result Codes

In

n=0 Product Code

Yn

n=0 Next Reset to &W0 settings

 

n=1 Checksum

 

n=1 Next Reset to &W1 settings

 

n=2 RAM Test

 

n=2 Next Reset to &F0 settings

 

n=3 Product ID string

 

n=3 Next Reset to &F1 settings

 

n=4 Current Settings

 

n=4 Next Reset to &F2 settings

 

n=5 NVRAM Settings

Zn

n=0 Y setting determines reset

 

n=6 Link Diagnostics

 

n=1 Reset to &W0 settings

 

n=7 Product Configuration

 

n=2 Reset to &W1 settings

 

n=9 PnP Enumeration Screen

 

n=3 Reset to &F0 settings

 

n=11 Link Diagnostics

 

n=4 Reset to &F1 settings

Ln

n=0 Low Speaker Volume

 

n=5 Reset to &F2 settings

 

n=1 Low Speaker Volume

+++

Escape Code

 

n=2 Med Speaker Volume

$

HELP, Command Summary

 

n=3 Hi Speaker Volume

~Zn

n=0 Normal

Mn

n=0 Speaker OFF

 

n=1 Enhanced

Modem Cellular Commands

&f5

Load cellular defaults

~Z

Toggle enhanced mode

&f6

Load ETC mode, wait for cellular call

Modem Dial Commands

0-9

Digits to Dial

,

Pause (Wait for S8 Time)

*

Auxiliary Tone Dial Digit

;

Remain in Command Mode After Dialing

#

Auxiliary Tone Dial Digit

"

Used to Dial Alpha Phone #'s

T

Tone Dialing

W

Wait for 2nd Dial Tone (X2,X4)

P

Pulse Dialing

@

Wait for an Answer (X3,X4)

R

Call an Originate Only Modem

!

Flash Switch Hook

/

Short Delay

   

Modem Ampersand Commands

&An

n=0 Disable /ARQ Result Codes

 

n=2 Xon/Xoff

 

n=1 Enable /ARQ Result Codes

 

n=3 CTS and Xon/Xoff

 

n=2 Enable /Modulation Codes

&In

n=0 Disable RX Flow Control

 

n=3 Enable /Extra Result Codes

 

n=1 Xon/Xoff

&Bn

n=0 Floating DTE Speed

 

n=2 Xon/Xoff Chars Filtered

 

n=1 Fixed DTE Speed

 

n=3 HP Enq/Ack Host Mode

 

n=2 DTE Speed Fixed When ARQ

 

n=4 HP Enq/Ack Terminal Mode

&Cn

n=0 CD Always ON

 

n=5 Xon/Xoff for non-ARQ Mode

 

n=1 Modem Controls CD

&Kn

n=0 Disable Data Compression

&Dn

n=0 Ignore DTR

 

n=1 Auto Data Compression

 

n=1 On-Line Command Mode

 

n=2 Enable Data Compression

 

n=2 DTE Controls DTR

 

n=3 Selective Data Compression

 

n=3 Reset ON DTR Loss

&Mn

n=0 Normal Mode

&Fn

n=0 Load Factory 0, HW FC

 

n=4 ARQ/Normal Mode

 

n=1 Load Factory 1, HW FC

 

n=5 ARQ Mode

 

n=2 Load Factory 2, SW FC

&Nn

n=0 Highest Link Speed

 

n=5 Load Factory 5, ETC_CELL

 

n=1 300 bps

 

n=6 Load Factory 6, ETC_LAND

 

n=2 1200 bps

&Gn

n=0 No Guard Tone

 

n=3 2400 bps

 

n=1 550 Hz Guard Tone

 

n=4 4800 bps

 

n=2 1800 Hz Guard Tone

 

n=5 7200 bps

&Hn

n=0 Disable TX Flow Control

 

n=6 9600 bps

 

n=1 CTS

 

n=7 12000 bps

 

n=8 14400 bps

&Tn

n=0 End Test

 

n=9 16800 bps

 

n=1 Analog Loopback (ALB)

 

n=10 19200 bps

 

n=3 Digital Loopback (DLB)

 

n=11 21600 bps

 

n=4 Grant Remote DLB

 

n=12 24000 bps

 

n=5 Deny Remote DLB

 

n=13 26400 bps

 

n=6 Remote Digital Loopback

 

n=14 28800 bps

 

n=7 Remote DLB With Self Test

 

n=15 31200 bps

 

n=8 ALB With Self Test

 

n=16 33600 bps

&Un

n=0 Variable link rate floor

 

n=17 28000 bps

 

n=1 Minimum link rate 300 bps

 

n=18 29333 bps

 

n=2 Minimum link rate 1200 bps

 

n=19 30666 bps

 

n=3 Minimum link rate 2400 bps

 

n=20 32000 bps

 

n=4 Minimum link rate 4800 bps

 

n=21 33333 bps

 

n=5 Minimum link rate 7200 bps

 

n=22 34666 bps

 

n=6 Minimum link rate 9600 bps

 

n=23 36000 bps

 

n=7 Minimum link rate 12000 bps

 

n=24 37333 bps

 

n=8 Minimum link rate 14400 bps

 

n=25 38666 bps

 

n=9 Minimum link rate 16800 bps

 

n=26 40000 bps

 

n=10 Minimum link rate 19200 bps

 

n=27 41333 bps

 

n=11 Minimum link rate 21600 bps

 

n=28 42666 bps

 

n=12 Minimum link rate 24000 bps

 

n=29 44000 bps

 

n=13 Minimum link rate 26400 bps

 

n=30 45333 bps

 

n=14 Minimum link rate 28800 bps

 

n=31 46666 bps

 

n=15 Minimum link rate 31200 bps

 

n=32 48000 bps

 

n=16 Minimum link rate 33600 bps

 

n=33 49333 bps

 

n=17 Minimum link rate 28000 bps

 

n=34 50666 bps

 

n=18 Minimum link rate 29333 bps

 

n=35 52000 bps

 

n=19 Minimum link rate 30666 bps

 

n=36 53333 bps

 

n=20 Minimum link rate 32000 bps

 

n=37 54666 bps

 

n=21 Minimum link rate 33333 bps

 

n=38 56000 bps

 

n=22 Minimum link rate 34666 bps

 

n=39 57333 bps

 

n=23 Minimum link rate 36000 bps

&Pn

n=0 N. American Pulse Dial

 

n=24 Minimum link rate 37333 bps

 

n=1 UK Pulse Dial

 

n=25 Minimum link rate 38666 bps

&Rn

n=1 Ignore RTS

 

n=26 Minimum link rate 40000 bps

 

n=2 RX to DTE/RTS high

 

n=27 Minimum link rate 41333 bps

&Sn

n=0 DSR Always ON

 

n=28 Minimum link rate 42666 bps

 

n=1 Modem Controls DSR

 

n=29 Minimum link rate 44000 bps

 

n=30 Minimum link rate 45333 bps

&Wn

n=0 Store Configuration 0

 

n=31 Minimum link rate 46666 bps

 

n=1 Store Configuration 1

 

n=32 Minimum link rate 48000 bps

&Yn

n=0 Destructive

 

n=33 Minimum link rate 49333 bps

 

n=1 Destructive/Expedited

 

n=34 Minimum link rate 50666 bps

 

n=2 Nondest./Expedited

 

n=35 Minimum link rate 52000 bps

 

n=3 Nondest./Unexpedited

 

n=36 Minimum link rate 53333 bps

&Zn=s

Store Phone Number

 

n=37 Minimum link rate 54666 bps

&Zn?

Query Phone Number

 

n=38 Minimum link rate 56000 bps

#CID=n

n=0 Caller ID Off

 

n=39 Minimum link rate 57333 bps

 

n=1 Formatted Caller ID

     

n=2 Unformatted Caller ID

Modem S Register Functions

S0

Ring to Answer ON

   

S1

Counts # of Rings

 

1 = MNP/V.42 Disabled in V.22

S2

Escape Code Char

 

2 = MNP/V.42 Disabled in V.22bis

S3

Carriage Return Char

 

4 = MNP/V.42 Disabled in V.32

S4

Line Feed Char

 

8 = Disable MNP Handshake

S5

Backspace Char

 

16 = Disable MNP Level 4

S6

Wait Time/Dial Tone (sec)

 

32 = Disable MNP Level 3

S7

Wait Time/Carrier (sec)

 

64 = Unusual MNP-Incompatibility

S8

Comma Time (sec)

 

128 = Disable V.42

S9

Carrier Detect Time (1/10sec)

 

136 = Disable V.42 Detect Phase

S10

Carrier Loss Time (1/10sec)

S16

Test Modes

S11

Dial Tone Spacing (msec)

 

1 = Reserved

S12

Escape Code Time (1/50sec)

 

2 = Dial Test

S13

Bit Mapped

 

4 = Reserved

 

1 = Reset ON DTR Loss

 

8 = Reserved

 

2 = Reduced Non-ARQ TX Buffer

 

16 = Reserved

 

4 = Set DEL=Backspace

 

32 = Reserved

 

8 = Do DS0 ON DTR

 

64 = Reserved

 

16 = Do DS0 ON Reset

 

128 = Reserved

 

32 = Reserved

S17

Reserved

 

64 = Disable Quick Retrains

S18

&Tn Test Timeout (sec)

 

128 = Escape Code Hang Up

S19

Inactivity Timeout (min)

S14

Reserved

S20

Reserved

S15

Bit Mapped

S21

Break Length (1/100sec)

S22

Xon Char

 

8 = Disable 3000 Symbol rate

S23

Xoff Char

 

16 = Disable 3200 Symbol rate

S24

Reserved

 

32 = Disable 3429 Symbol rate

S25

DTR Recognition Time (1/100sec)

 

64 = Reserved

S26

Reserved

 

128 = Disable Shaping

S27

Bit Mapped

S34

V.34 & V.34+ Connection setup

 

1 = V21 Mode

 

bit mapped control flags

 

2 = Disable TCM

 

1 = Disable 8S-2D trellis encoding

 

4 = Disable V32

 

2 = Disable 16S-4D trellis encoding

 

8 = Disable 2100hz

 

4 = Disable 32S-2D trellis encoding

 

16 = Enable V23 Fallback

 

8 = Disable 64S-4D trellis encoding

 

32 = Disable V32bis

 

16 = Disable Non-linear coding

 

64 = Reserved

 

32 = Disable TX level deviation

 

128 = Software Compatibility Mode

 

64 = Disable Pre-emphasis

S28

V.32 Handshake Time (1/10sec)

 

128 = Disable Pre-coding

S29

V.21 answer mode fallback timer

S35

Reserved

S30

Reserved

S36

Reserved

S31

Reserved

S37

Reserved

S32

Connection bit mapped operations

S38

Disconnect Wait Time (sec)

 

1 = V.8 Call Indicate enable

S39

Reserved

 

2 = Enable V.8 mode

S40

Reserved

 

4 = Reserved

S41

Distinctive Ring options

 

8 = Disable V.34 modulation

 

1 = Distinctive Ring Enabled

 

16 = Disable V.34+ modulation

 

2 = Reserved

 

32 = Disable x2 modulation

 

4 = Reserved

 

64 = Disable V.90 modulation

 

8 = Reserved

 

128 = Reserved

 

16 = Reserved

S33

V.34 & V.34+ Connection setup

 

32 = Reserved

 

bit mapped control flags

 

64 = Reserved

 

1 = Disable 2400 Symbol rate

 

128 = Reserved

 

2 = Disable 2743 Symbol rate

S42

Reserved

 

4 = Disable 2800 Symbol rate

   

Most laptop users never make use of their modem's AT commands, but some of these commands can be quite handy. For example, the command ATM0 turns off the modem's speaker.

Tip

If you don't have a table of modem commands with you, most modems will generate one up for you via the following commands:

  • AT$ HELP, Command Summary

  • ATD$ HELP, Dial Commands

  • AT&$ HELP, Ampersand Commands

  • ATS$ HELP, S Registers

When I get a modem, I go into the Windows HyperTerminal, execute all these help commands, one after another, and capture the output to a file. Then I clean up the file a bit with an editor, resulting in a nice, handy little reference for the modem! In the old days I used to print the charts in as small a font as possible and then cut and laminate it to produce a durable reference card.


How to Use the AT Command Set

To control a modem directly with AT commands, you will need to use a terminal-emulation program. All versions of Windows are bundled with a useful terminal emulator called HyperTerminal, published by Hilgraeve. To access your modem, you will have to know which communications or COM port it is using. To find the COM port in Windows XP, do the following:

  1. Go to the Control Panel in Windows XP (click Start, Control Panel).

  2. Enable Control Panel's classic icon view (click the Classic View text on the left side of the screen) and double-click the Phones and Modems Options icon.

  3. Click the Modems tab.

  4. Identify the modem in the list and note the number of the COM port to which it is attached (see Figure 12.10).

    Figure 12.10. A dialog box showing where to find the COM port for a modem under Windows XP.

    graphics/12fig10.gif

In other versions of Windows, the procedure differs but is similar.

Once you know the COM port, you can access the modem using HyperTerminal by doing the following in Windows XP:

  1. Click Start, All Programs, Accessories, Communications, HyperTerminal (the program, not the folder).

  2. A New Connection dialog box will appear. Enter a name for the new connection, such as Access The Modem, and select an appropriate icon (see Figure 12.11).

    Figure 12.11. The New Connection dialog box of the HyperTerminal program bundled with Windows XP.

    graphics/12fig11.gif

  3. A Connect To dialog box will appear. Disregard the text boxes asking for country, area code, and phone number. At the drop-down box labeled Connect Using, select the COM port, such as COM3 (see Figure 12.12).

    Figure 12.12. The HyperTerminal dialog box showing how to access a particular COM port.

    graphics/12fig12.gif

  4. A dialog box (see Figure 12.13) will appear asking for the properties of the COM port you have selected. Enter a speed of 57600 or similar (the exact speed is unimportant here). Leave the default values for Data Bits (8), Parity (None), Stop Bits (1), and Flow Control (Hardware).

    Figure 12.13. The HyperTerminal dialog box showing how to change port settings.

    graphics/12fig13.gif

  5. A HyperTerminal window will appear. Type AT and hit the Enter key. You should see AT echoed on the screen, followed by the modem's response, "OK." This indicates that the modem is connected and functioning (see Figure 12.14).

    Figure 12.14. The HyperTerminal dialog box showing a modem responding "OK."

    graphics/12fig14.gif

  6. You can use any of the AT commands. For example, to dial a number, enter ATD 555-1111 and you should hear the modem dialing ( assuming you haven't disabled the modem's speaker, of course).

You can now use commands such as ATI0, ATI1, ATI2, and so on, to see how they can be useful to determine what modem you have, which firmware levels are installed, to run diagnostics, and so on. If you know the phone number of a computer system, you can now dial it and interact with it.

Tip

If you're not sure whether a phone line is live or dead, try this simple test: Use HyperTerminal to access your modem and then enter the following modem command: ATD. If you don't hear a dial tone, there is something wrong with the phone line or your connection to it.


Acoustic Couplers

On those occasions when you can't plug your modem into the phone jack, or when no jack is available (such as at a pay phone), the last resort is an acoustic coupler . The acoustic coupler is an ancient telecommunications device that predates the system of modular jacks used to connect telephones today; you might have seen a very young Matthew Broderick use an acoustic coupler in the 1983 movie War Games . To connect to a telephone line, the coupler plugs into your modem's RJ-11 jack at one end and clamps to a telephone handset at the other end. A speaker at the mouthpiece and a microphone at the earpiece allow the audible signals generated by the modem and the phone system to interact.

An acoustic coupler is difficult to work with. Any loud ambient noise can slow down your connection. Even a slight touch of a finger to the handset can cause problems. The acoustic coupler can also be an annoying and bulky bit of extra baggage to have to carry with you, but it is the one foolproof method for connecting to any telephone line without having to worry about international standards, line current, or wiring.

Acoustic couplers are still available from a company called Konexx (www.konexx.com). That company's Koupler is available for $149.

Wire-It-Yourself

In the early days of the personal computer revolution, laptop users would often find themselves staying in hotel rooms that were not equipped with modular phone jacks. To handle such situations, I would carry a small screwdriver and special phone cable with a modular phone jack at one end and a pair of alligator clips at the other. To make a connection, I would locate the phone jack (which was usually behind a heavy, hard-to-move bed), unscrew the cover of the phone jack, and attach the alligator clips to two of the terminals underneath. A dial tone on the laptop's modem would signal that I had connected to the correct pair of terminals.

Nowadays, it is hard to find a hotel room that does not have a modular phone jack, let alone a convenient jack that is specially designed for use with a laptop. To handle those very rare situations where a modular phone jack is missing, you will be better off carrying a cable to connect your laptop to your cell phone. The way some hotels gouge their guests for local calls, the cellular data connection may actually save you money.



Upgrading and Repairing Laptops
Scott Muellers Upgrading and Repairing Laptops, Second Edition
ISBN: 0789733765
EAN: 2147483647
Year: 2003
Pages: 182
Authors: Scott Mueller

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