EZ_Online NO_MODEM.TXT 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� No modem ... no phone connection? Going online means, connecting your computer to another computer using the telephone lines. Computers deal in digital data, which is represented by only two signal states ... 0 and 1, high and low, on and off. Conventional telephone systems are designed for voice communications, which involve audible, continuously variable, electrical signals, and cannot transmit two-state digital information. The problem of transmitting digital information was easily and intuitively solved, by simply converting the two states of the transmitting computer's signals to different sounds, passing them into the phone system and sending them to a computer on the other end of the line, where they're converted from sounds back to two-state digital pulses. The tool that does this is called a "MODEM", an acronym for MOdulate/DEModulate. Modems can be internal or external. If you have an external modem (not common), you'll find a separate box with several little lights plugged into the back of your computer. More likely, your modem will be internal ... a board plugged into one of the slots inside your computer, with modular telephone connectors protruding through openings in the back of its case. If you find phone connectors on the back of your computer's case, simply connect the one marked "Line" to the nearest wall connector. If needed, standard telephone cables, extensions, and couplers are available at Radio Shack stores, hardware stores and discount department stores. Naturally, this assumes that your phone system is properly wired. If there's any doubt about it ... you'll notice that your phone cable has four wires: RED, GREEN, YELLOW and BLACK. Also notice that the phone connectors have four pins, then assure that the RED and GREEN wires are connected to the middle two pins. If your computer is not modem-equipped ... not to worry! You can probably afford, and install, an internal modem. What to buy? Modems are also classed by transfer speed, and at the present time 28,800 "baud" (bits per second) units are the creme of the crop. If you can afford it, spending $180 now will surely save you much more that that in phone bills over the life of the equipment ... and while you're at it, make it a FAX/Modem ... it won't cost any more, and you'll be able to send FAX's directly from your computer, should you ever wish to do so. If you'd rather not open your computer's case, another $30 will get you the external version of any internal fax/modem. For $100 less, about $96, you can purchase a 14,400 baud unit, which is obviously slower, but still quite adequate. If you look hard enough, you'll be able to find a 9,600 baud internal modem for about $45, and this may be good enough for now. If you have only pocket change, a 2,400 baud modem is certainly better than nothing, and shouldn't cost more than about $15 ... and you might even be able to find one of these older, but still perfectly functional units, available as a gift from a friend who upgraded to a faster unit. To install an internal modem, you need only open the case of your computer and plug it in at any available "slot". You will also probably need to "tell" the board which "COM port" and "Interrupt" it may use, and this is usually done either by moving jumpers on the board, or setting its "dip switches" according to directions provided with the unit. What's a "COM port"? What's an "Interrupt"? Internally, your computer moves data around in eight-bit "bytes" on a wiring system composed of parallel lines. Moving all these bits simultaneously on parallel lines greatly speeds things up, compared to transmitting eight-bit "bytes" one bit at a time on a single line. But since telephone lines can only carry one bit at a time, the computer has to convert its "parallel" data to "serial" (one bit at a time). This task is performed by a chip known as a Universal Asynchronous Receiver/Transmitter (UART). The computer sends this chip 8-bit bytes on its parallel wires, and the chip passes them on to your modem as a stream of bits on a single line. The UART works in reverse also, converting serial bit streams received from your modem to 8-bit parallel bytes and sending them on to your computer. The UART is also referred to as a "serial port", aka "COM port". Your computer probably came with a single UART, which serves your mouse. Your modem contains its own UART, so now you'll have two. DOS can handle up to four COM ports, and you can designate your UART's as you wish, as COM1, COM2, COM3 or COM4 ... the name doesn't have any relation to the actual physical connection of the UART, its simply a handle that DOS uses to identify the serial ports. By convention, COM1 is now usually assigned to the UART that serves your mouse, and COM2 to your modem. Since handling data serially is a much slower process than moving the same data on a "parallel bus", the computer is able to move data much faster than the UART. A system of "handshaking" has thereby been devised to let the UART "talk to" the computer, telling it when to stop sending data, when it has data available, and so on. To permit the computer to do other work while the UART is slowly doing its work, this "interrupt" technique is employed, whereby the UART is able to send a signal on a special line ... the IRQ line ... to get the computer's attention when it's finally ready to receive more data, or to send data to the computer. If your setup is typical, you have a mouse on "COM1", and you'll want your modem to use "COM2". The default interrupt for COM2 is "IRQ3" ... and that's all there is to that. A dip switch setup on the back of your modem (near the phone connectors) is pretty much standard; if necessary, just change the switch settings to the proper positions shown for COM2. Naturally, you can't have two devices assigned to the same port at the same time. If you're not sure about your mouse, use its diagnostic software (usually found in a "C:\MOUSE" directory) to see if its been assigned COM1 or COM2. Beyond that, installing an internal modem is probably the easiest add-on project you'll ever do. So approach the project with confidence. You can do it! Evil-Crypt BBS Tony Zarzecki, SysOp Redford, MI usa 313-538=3762 (to exit, touch Esc ... then "Y")