Multi Tech Equipment manual MultiModemISI Hybrid Series, ISIHI-2S 171

Glossary

Automatic Dialer: A device which is programmed to place a call to a predetermined number any time it is taken “off- hook”.

B

Background: An activity that takes place in the PC while you are running another application. In other words, the active user interface does not correspond to the ‘back- ground’ task. In Windows™, the area behind the active window. Compare with foreground.

Backup: Additional resources or duplicate copies of data on different storage media for emergency purposes.

Band: The range of frequencies between two defined endpoints.

Bandwidth: The transmission capacity of a computer channel, communications line or bus. It is expressed in cycles per second (hertz), the bandwidth being the differ- ence between the lowest and highest frequencies transmit- ted. The bandwidth of a phone line is about 3000Hz with QAM, you get up to 14,400 bps. Bandwidth is often stated in bits or bytes per second.

Baseband signal: An unmodulated signal which is trans- mitted at its original frequency and may be digital or analog.

Baud: Rate, the signaling rate of a line, the switching speed, or the number of transitions (voltage or frequency changes) that are made per second. Transmission speeds are often expressed in baud, though bits per second is more accurate. The speed at which your computer talks to your modem.

BCC (Block Check Character): An error control method used in character-oriented or byte-synchronous protocols. Two 8-bit BCCs are used to create the CRC (Cyclic Redun- dancy Check) field of a synchronous data packet.

Bell 103: The U.S. modulation standard for 300 bps full- duplex transmission over dial-up lines.

Bell 201: The U.S. modulation standard for 2400 bps half- duplex transmission over dial-up lines or full-duplex trans- mission over 4-wire lines. Primarily used in synchronous modems.

Bell 202: The U.S. modulation standard for

0-1200 bps, half-duplex transmission over 2-wise, or full- duplex transmission over 4-wire leased lines.

Bell 208: The U.S. modulation standard for 4800 bps, half- duplex transmission over dial-up lines, or full-duplex trans- mission over 4-wire lines. Primarily used in synchronous modems.

Bell 212A: The U.S. modulation standard for 1200 bps full- duplex transmission over dial-up lines.

Binary: A numbering system based on two digits, 1 and 0, which is conductive to the two-state digital electronics used within computers. All input to a computer is encoded as a

binary value. Binary also refers to a file format that uses 8- bit characters , to allow for control characters (i.e., all non- ASCII files).

BSC (Binary Synchronous Communications): Also called “bisync”, this communications protocol was the first synchronous data format used by IBM. It is still in use, but is rapidly being replaced by IBM’s newer Synchronous Data Link Control (SDLC). Bisync is a byte-synchronous protocol that has longer delays and more overhead that the bit- synchronous SDLC. It uses two synchronization characters to head every packet.

Bit (Binary DigIT): A bit is the basis of the binary number system. It can take the value of 1 or 0. Bits are generally recognized as the electrical charge generated or stored by a computer that represents some portion of usable informa- tion.

Bit-synchronous transmission: A synchronous form of data transmission that focuses on a maximum packet size rather than the length of the characters the packet contains. SDLC is a bit-synchronous protocol.

Boot: Starting or restarting your PC. This term originates from the saying “to pull oneself up by the bootstraps”.

Bps (bits per second): A unit to measure the speed at which data bits can be transmitted or received. Bps differs from baud when more than one bit is represented by a single cycle of the carrier.

Break-out box: An electronic device which is inserted between two RS232/V.24 connectors for the monitoring of pin activity and for the re-routing of lines (crossover).

Broadcast: To send information simultaneously to a group of recipients.

Buffer: A temporary storage register or Random Access Memory (RAM), used in all aspects of data communications which prevents data from being lost due to differences in transmission speed. Keyboards, serial ports, muxes and printers are a few examples of the devices that contain buffers. A buffer allows one device to dump data at a high speed and for the lower-speed device to accept it at its own pace. In this way, the high-speed device can continue to work without having to wait for its data transfer to end. Buffers are a way of preventing potential data loss.

Bus: A common channel between hardware devices either internally between components in a computer, or externally, between stations in a communications network.

Byte: The unit of information a computer can handle at one time. The most common understanding is that a byte consist of 8 binary digits (bits), because that’s what comput- ers (PCs) can handle. A byte holds the equivalent of a single character, such as the letter “A”.

MultiModemISI Hybrid Series, ISIHI-2S 171