'Common Terms' Terms and Definitions Common to Telecommunications The following is a list of terms you should know before you dive into telecommunications. The basic definitions cover the major points you will need to know in order to get the most out of this program. AutoAnswer - This is a feature that most Hayes compatible modems support. It allows people to call your modem, and it will pick the phone up automatically and start communicating with the other modem. This is useful if you plan to run a bulletin board system. AutoDial - This is a feature of some modems that allows the modem to dial the telephone itself and attempt to connect to the modem on the other end. Baud - It is commonly misused as a synonym for bits per second. We will use it to mean the measure of modem speed throughout this tutorial. Baud is named after the inventor Emil Baudot, who invented the teletype in 1882. The Amiga serial port is capable of speeds exceeding 31,250 baud, although speeds of this magnitude are almost never used. Bits + Bytes - A bit is the smallest possible value the computer will use internally. A bit has two possible positions, 1 or 0 (on or off). A byte is 8 bits, a K or kilobyte is 1024 bytes, and a megabyte is 1024K. Bulletin Board System (BBS) - A service provided by a person (called the System Operator or Sysop) to others, whereby they connect their computers to the Sysop's with a modem and transfer data between them. This is usually in the form of messages to other users who use the system, or in the form of files (actual programs you can transfer between the BBS and your computer). Carrier - This is the noise that the modem generates to send and receive data. It sounds like a high pitched beep, but changes as data is transmitted. The carrier detect settings determine how your terminal program and modem react to the carrier signal. A terminal or BBS program uses the carrier detect signal to determine whether or not it is connected. CMOS Ram - Certain modems use a special memory chip that stores the configuration of the modem after it is turned off. The configuration will be recalled when the modem is turned back on. Without this memory the modem configuration must be set up each time it is turned on. Data Terminal Ready (DTR) - This is a signal that lets the modem know if the computer is, or isn't ready. It can be set so that the modem believes that the computer is always ready, this is called ignoring the DTR. It can also be set so that the modem responds to changes in the DTR. DTR is commonly turned on, or high, when the computer opens the serial port, and turned off, or brought low, when the computer closes the serial port. This is usually done in terminal and BBS programs. Many BBS programs use the DTR to hang up the modem and to disable auto answer when the sysop is using the system. DIP Switches - These are little switches on the modem. These switches will configure the modem settings, such as whether to force DTR etc. They have since become obsolete with the advent of CMOS RAM storage for the same settings. Downloading - Downloading is the receiving of a file from another computer to yours over a telephone line with a modem. It is usually done with an error checking and correcting protocol such as Xmodem, Ymodem, or Zmodem which will be discussed later on in the tutorial. Duplex - This describes the method of sending/receiving data in telecommunications. When using full duplex, you can send and receive at the same time, similar to a telephone conversation. When you select half duplex you can only send or receive at one time, but not both. This is similar to many CB radios. The computers will know which they should be doing (sending or receiving) by use of flow control (see below). Flow Control - Flow control consists of internal codes used by the computer to control the receiving of data. Usually, so it can catch up to the computer sending the data on the other end. The most common method of flow control is XON/XOFF. This is where a CTRL-S is sent to stop the other computer, and a CTRL-Q is sent to restart it. Anyone typing into a terminal program can also usually send these codes. This could be used to catch up on reading the text on the screen. Other methods include CTS/DTR, which is mainl used by serial printers and high speed modems. HST - This is a type of modem manufactured by US Robotics. It runs at speeds exceeding 9600 baud. Its main problem is that it can only communicate with another HST modem at 9600 baud or above. That is the reason BBSs using HST modems are marked HST. Modem - A modem is a MODulator/DEModulator. When a modem transmits data it turns the data into audible tones that can be transmitted over the telephone wires. When the modem receives data it converts these audible tones back into its original form. This is used to transfer data between computers. This is the main focus of TeleTutor. Multiuser - This is a computer that allows multiple users to be logged on at the same time. This term is sometimes combined with multitasking. This means that the computer can perform multiple operations at once. The Amiga is multitasking and can be made to be multi-user with the help of a network or a modem. On/Off Hook - This is the determination of whether the modem is using the phone line. You can think of this as the modem picking up the phone (off hook), and the modem hanging up the phone (on hook). PBX - This is a network of telephones, usually in an office complex. A PBX would be a system where you have to dial a number (usually 9) to get access to an outside line. Protocols - Protocols are the methods used to transfer files over a modem between two or more computers. The most popular ones are, in order of popularity, Xmodem, Ymodem, Zmodem, Wxmodem, Kermit, B Protocol, etc. Pulse Dialing - This is the term used to describe a phone line where dialing is done by putting the phone on hook and then off hook quickly. Rotary phones are an example of this, and phones that click a certain number of times when a number key is pressed on the phone. Settings - These include the following terms: Data, Parity, and Stop bits. Data Bits: These are the number of bits being sent, usually 7 or 8 bits. Eight will send the full 255 ASCII codes. The last 127 may differ from computer to computer and is usually where special graphics characters are put. Seven bits will only send the first 127 codes which are the actual letters and some special characters like the bell and the flow control characters. Parity: This is a number sent along with each block of data used as a check. It has a few parameters: odd, even, space, or none. None: This means that there is no parity check. Even: This means an even code is sent. Odd: This means a odd code is sent. Space: This means a space is sent. These are then checked against what was received to assure data integrity. Stop bits: These are the number of bits trailing the block of bits. The most often used settings are 8N1 (8bits, no parity, 1 stop bit), and 7E1 (7bits, even parity, 1 stop bit). You will use 8N1 in most cases. Terminals - A terminal (on the Amiga) is a program that lets the Amiga communicate with a modem. It is also referred to as a terminal emulator, but only when it emulates the way a real terminal works, such as a DEC VT-100 or an HP terminal. These are used primarily to connect to other computers, usually large multiuser ones, such as mainframes and minicomputers. Touch Tone Dialing - This is telephone service where the line is dialed quickly with a series of tones instead of putting the line on and off hook quickly as is done with pulse service. Every telephone has pulse service. Touch tone may not be available in some areas or may be an added expense. Uploading - The sending of a file from your computer to another one over a telephone line with a modem. It is usually done with an error checking and correcting protocol such as Xmodem, Ymodem, or Zmodem discussed later in the tutorial. Copyright © 1989 - By Cole Calistra