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Aptiva - Communications terms
Applicable to: World-Wide
Service Information: Now that computers have a major impact on our lives, you may have at one time or another found yourself trying to understanding computer terminology. Communications seems to be one of the most confusing. The article below touches on some of the major terms used in the communications arena, and will hopefully clear the "lines of communication" a little.
The MODEM - An inside look:
Before your computer can begin to communicate with another computer, you must have the necessary hardware. A MODEM (contraction for MOdulator/DEModulator) is a device that allows your computer to talk to another computer by means of a phone line.
The MODULATOR inside the modem translates the computer's DIGITAL data into ANALOG data so that it can travel over the phone line, where the DEMODULATOR receives the ANALOG data from the phone line and converts it back to DIGITAL data so the computer can understand it.
The computer sending the information is called the HOST computer and the computer receiving the information is called the REMOTE computer. The HOST computer can also communicate via a modem with a TERMINAL computer which usually consists of a VIDEO DISPLAY and a KEYBOARD. A terminal used in a multi-user system does little or no computing of its own.
Modems can be either INTERNAL or EXTERNAL. The EXTERNAL modems are usually easier to install as they are attached to the computer via a data cable and are designed to sit outside the body of your computer. INTERNAL modems are located inside the body (or case) of your computer. Internal modems are expansion boards which are plugged into an empty expansion slot inside your computer.
There are four major parts to every modem:
1. The DATA TERMINAL EQUIPMENT interface (or DTE) lets the modem communicate with the computer digitally. Internal modems communicate with the computer digitally via the computer's DATA BUS, which the modem comes in contact with through the expansion slot. A data bus is the channel that data follows to reach the CPU (Central Processing Unit) or "the brain of the computer". If the modem is external, the DTE communicates with the CPU through an RS-232 cable attached to an external serial port.
2. The CONTROLLER is basically the modem's microprocessor (or "brain"). It is used to interpret commands from the modem's COMMUNICATION SOFTWARE (to be discussed later) that tells the modem how to handle the data. The controller does a lot of ERROR CONTROL (making sure the data is transferred completely and correctly), and DATA COMPRESSION (compacting the data so that more information can be transferred at a one time).
3. The MODULATOR/DEMODULATOR mentioned earlier, takes the computer's digital information and converts it to analog information so that it can be sent over the phone lines. The modulator/demodulator is also responsible for reversing the analog data back to digital so that it can be used by the computer.
4. The LINE INTERFACE is the used to make sure the signals from the modem and the phone line match up so the data can be transmitted properly. The line interface is also important to the modem because it protects the modem from being damaged by the high voltages of electricity used to make the phone ring.
A modem is usually categorized by how fast it can process data. The measurement of speed used by modems is called BITS PER SECOND (or BPS). As you may know, a computer runs on a digital signal, which is a definite ON or OFF (0 or 1). Each of those ONs or OFFs is a BIT (the smallest unit of measurement for a computer). Therefore modems are rated by how many of these bits they can transmit over the phone line per second. The most common speeds are 28800, 33600, and 56000 bps. Some computer users confuse bps with the term BAUD RATE. Baud rate refers to how many events or signal changes the modem can transmit in one second. The reason the baud rate of the modem can differ from the bps rate is that one signal change can actually include more than one bit of information. (Note: at present no analog phone lines support a true 56000 bps connection. The Aptiva models which support 56k download speeds are compatible with the K56Flex protocol. Currently there are two standards being used in the industry for 56k connections, they are K56Flex (Rockwell, Lucent) or X2 (USR).
Most major computer manufacturers including IBM, Compaq and HP, made the decision some time ago to support the K56Flex protocol. This was largely due to the stability and reliability of the connection at the highest speed available. Also, K56Flex was the only technology which properly supported the telephony features we planned to offer our customers.
In the Internet Service Provider (ISP) and Online Services communities, the effort has been to support both protocols. Currently, most ISP's support both, and most others plan to support both within the next few months. Online services, including America Online, now support both protocols. IBM Global Network (IGN) adopted the X2 protocol, exclusively, and have no plans for supporting both protocols in the near future. To determine which protocol your ISP supports, contact your ISP. Most ISP's now have sections on their websites to detail the protocols supported and what areas or phone numbers they offer them through. You can also find more information on these protocols by visiting any of the following websites:
http://x2.usr.com/
http://www.lucent.com/micro/k56flex/
The industry is also working to develop a new 56k standard to resolve this issue. This new technology is expected to be available early in 1998. Once available, IBM will work to make this new technology available to our new and existing customers. Until this new technology is available, you will need to use an ISP or Online Service which offers the K56 protocol in order to obtain the higher download speeds. You can also use the K56 ISP search feature on the Lucent webpage (http://www.lucent.com/micro/k56flex/isp.html) to find a K56 provider in your area.)
Because not all modems work at the same speed, you will not always have the same speed modem as the computer you are communicating with. In order for different types of modems to communicate there is exists a sort of rule or code called CONNECT SPEED that modems will follow. When your modem communicates with another modem, it connects at the highest speed that they have in common. In other words, if your modem runs at 28800 bps and the modem that you are calling runs at 33600 bps, the information can only be transferred at up to 28800 bps because that is the highest speed the two modems have in common.
The two modems determine connect speed and other important factors when they first communicate. This point of communication is called HANDSHAKING, much like two people do when meeting and saying hello. During handshaking, the two modems tell each other what speed they are running, confirm if they both have error correction and data compression. The connection is then based on these factors.
Communication between the modems is also controlled by other rules that dictate the conversation between the two modems. These "chaperons" of sorts are called COMMUNICATION PROTOCOLS. Other than specifying the format in which the data is presented, the protocol also controls when the sending modem can speak and when the receiving modem can respond. After the modems have finished their "small talk", they can get on to the more serious business of swapping information called UPLOADING or DOWNLOADING. Uploading is the process of sending a file from "your" computer to the other modem-equipped computer. Downloading is the process of receiving a file from the "other" computer.
What is a FAX/Modem?
While modems are great for communicating messages and files, FAX/Modems allow users to send documents to another computer (also with a FAX/Modem) or a FAX machine without ever leaving their computer. In essence the FAX/Modem is a combination FAX machine and a data modem, and they install exactly the same way as the standard modem.
Unlike the FAX machine, your documents are converted to IMAGE files and sent via the FAX portion of the modem to a remote location where they are either printed by a FAX machine or saved as an image file on another computer with a FAX/Modem. The draw back to this type of faxing is when someone sends a FAX to your FAX/Modem, it is just like the ones you would receive from a FAX machine in that you can't edit it (unless you retype it into your computer). However you can edit a faxed document with the help of a OPTICAL CHARACTER RECOGNITION (or OCR) software. OCR software translates the faxed document into a text-based document that you can manipulate. These packages are usually stand-alone programs that can't send or receive faxes by themselves, although some of the newer FAX software packages do add this ability.
Online Services - Connecting you to the World
Not only can your computer (with the help of a modem) connect to another computer for the transfer of messages or files, but you can also tap into large databases of information on anything from research to news or interactive games. These large information distributors are called ONLINE SERVICES. Usually there is a fee involved in connecting to these types of services as well as some sort of subscription.
Most users pay a flat fee per month for access and either a per minute or per hour connect charge. Some of the more popular services are PRODIGY, AMERICA ONLINE, COMPUSERVE and GENIE.
When you are connected to an online service, you are considered ONLINE. When you disconnect, you are OFFLINE. The process of getting onto the service is called LOGGING ON or SIGNING ON, and the process of leaving or exiting the service is called SIGNING OFF or LOGGING OFF. There is generally an account and a password required for connecting to these types of services. Many of the online services offer features like electronic meeting rooms (or FORUMS) where users can chat as a group with specific interests or topic of discussion. Online service users generally have the ability to send and receive ELECTRONIC MAIL (or E-MAIL) in the form of messages and sometimes files. Many of the online services also offer an area called a BULLETIN BOARD, much like the bulletin board in your school or office. Usually abbreviated BBS, this area is used to post messages or notes for others users to read (i.e. asking for help, selling your car, buying a house, etc.)
Providing for the masses - File types do vary
There are three different types of files that are generally available from online services, PUBLIC DOMAIN, SHAREWARE and DEMOWARE.
1. PUBLIC DOMAIN - These programs are like public parks, anybody can have access to downloading them for no extra charge (only paying for connect time). You can use these files with no strings attached.
2. SHAREWARE - This category covers programs that smaller developers usually write with the intentions of making the public aware of the program. Once you have had a chance to load and evaluate the software, there is usually a REGISTRATION FEE which provides technical support or the developer will send you additional information about the software or an upgraded version of the software.
3. DEMOWARE - Most often demoware is a program that is taken from a larger commercial package, that you can "test drive" at no cost.
Getting it all to work together - Communication Software
Now that you have a little idea about the Hardware side of computer communications, let's take a look at the software side. COMMUNICATIONS SOFTWARE is the software needed by your computer's hardware in order to connect to another computer via modem. The software works with either modem- equipped computers or with computers connected through a direct connect cable. Most often the communications software is included with the modem or FAX/Modem at the time of purchase. This software usually handles the basic needs and is all you need to get started with a modem. There are also more sophisticated packages available that add advanced features and enhancements that you may want to look into after you become more familiar with computer communications.
Before you can use your modem with the communications software for the first time, you will need to CONFIGURE (or customize) the software. Configuring the software tells the software what type of hardware you are using, where the modem is located, and the maximum speed you can transfer data. Other settings that are usually required during the configuration process are DATA BITS, STOP BITS and PARITY. When your computer sends out the bits of information (eight DATA BITS, or one BYTE for each character) to the other computer, it will send a PARITY BIT along with the other bits. The PARITY BIT is used to ensure accuracy when the bits are transmitted. A STOP BIT is also sent with the bits that compose a character. The stop bit signals the end of the character to the other computer. Most communications software packages contain a DIALING DIRECTORY. This feature is handy when you use the program often and do not want to have pieces of paper all over your desk to keep up with phone numbers. Often the dialing directory will allow you to save settings necessary for each of the numbers that you dial, such as password, speed and hours of operation.
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Modems, General Information | |
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Date Created |
22-12-97 | |
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Last Updated |
04-01-99 | |
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Revision Date |
04-01-2000 | |
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IBM Aptiva | |
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Aptiva | |
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2134, 2136, 2137, 2138, 2139, 2140, 2142, 2144, 2153, 2156, 2158, 2159, 2161, 2162, 2163, 2164, 2168, 2176 | |
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