Multi Tech Equipment ISIHI-2S manual Glossary

Glossary

A

AC (Alternating Current): A power source whose signal crosses a reference voltage (usually called ground or zero). Alternating between a maximum and minimum voltage, AC may also be referred to as a bi-polar signal.Contrast with DC.

ACK (ACKnowledgment code – pronounced “ack”) : A communications code sent from a receiving modem to a transmitting modem to indicate that it is ready to accept data. It is also used to acknowledge the error-free receipt of transmitted data. Contract with NAK.

ACS (Asynchronous Communications Server): A communications server that managers a pool of modems for shared use over the LAN. It directs outgoing messages to the next available modem and directs incoming mes- sages to the appropriate workstation. It also provides conversion between LAN packets and asynchronous format.

Address: A numbered location inside a computer. It’s how the computer addresses its resources, like a video card, serial ports, memory, etc.

Algorithm: A set of ordered steps for solving a problem. This can be a mathematical formula or the instruction in a computer program.

Alphanumeric: The basic character set which includes the letters A to Z (and a to z) and the digits 0 to 9.

Amplitude: The difference between the maximum and minimum voltages of a waveform expressed as a “peak-to- peak” voltage.

Amplifier: An active device within a circuit which increases the voltage level of all signals (desirable and undesirable).

Analog loopback: A modem diagnostic used to test either the local analog loop (the modem’s internal circuitry) or the remote analog loop (the telephone line). The local analog loop test is accomplished by activating the self-test mode and tying the modem’s modulator to its demodulator and examining the return stream of data at the PC or terminal it services. The remote analog loopback can only be activated on four-wire leased line connections with a remote modem capable of performing the same test.

Analog signal: A waveform which has amplitude, frequency and phase, and which takes on a range of values between its maximum and minimum points. Analog implies continu- ous movement from point A to point B, as opposed to discrete jumps. For example, sound is continuously varying air vibrations and is converted into analogous electric signals to be carried on a telephone line.

Analog Transmissions: One of two types of telecommuni- cations which uses an analog signal as a carrier of voice, data, video, etc. An analog signal becomes a carrier when it is modulated by altering its phase, amplitude and frequency

to correspond with the source signal. Compare with digital transmission.

ANSI (American National Standards Institute – pro- nounced “ansy”) : A U.S. standards organization supported by over 1000 companies and trade organizations. It is a non-profit,non-government group that is the U.S. member of the ISO (International Standards Organization).

ANSI character set: An 8-bit character set that contains 256 characters. The first 128 characters are alphanumeric and the second 128 contain math and foreign language symbols.

API (Application Programming Interface): The language and message format used by a program to activate and interact with functions in another program or in the hard- ware. A software module which provides a uniform interface for otherwise incompatible programs.

ASCII (American Standard Code for Information Inter- change – pronounced “askey”) : A binary code for data that is used in communications and in many computers and terminals. The code is used to represent numbers, letters, punctuation and control characters. The basic ASCII code is a 7-bit character set, which defines 128 possible characters. The extended ASCII file provides 255 characters.

Associate: Establishing that all files with a given extension are usable by a certain application.

Asynchronous Transmission: The transmission of data in which each character is a self-contained unit with its own start and stop bits. This is a common method of transmis- sion between a computer and a modem. One character at a time, encoded into a series of electrical pulses, is transmit- ted or received. This is the oldest method of data transfer. When it is used with error correcting software and data compression algorithms, along with the increase it maxi- mum attainable speeds, it continues to be a viable alterna- tive to synchronous transmission.

ATM (Asynchronous Transfer Mode): A high speed switching technique suitable for MAN’s (Metropolitan Area Network) and broadband ISDN transmission.

Auto Answer: A modem feature which enables the modem to “off-hook” when it detects an incoming call.

Auto Dial: Some modems provide this feature for asyn- chronous dialing. This feature is a pre-defined macro that allows the user to enter the location of a phone number (i.e. N0 through N9) and have the modem go off-hook, dial and establish the connection. With the auto dial feature, an asynchronous terminal can establish a dialing directory without running a communication software package.

AUTOEXEC.BAT (AUTOmatic EXECute BATch): A DOS batch file that executes when the computer is started. This file contains the basic start-up commands that help config- ure the system.

170 MultiModem ISI Hybrid Series, ISIHI-2S