| COMMUNICATIONS GLOSSARY I |
Baud
- This is a switching speed or signaling rate of a line. It refers to the number of transitions (frequency changes) made per second. Baud equals to bits per second at only low speeds. (e.g., 300 baud is the same as 300 bps. However, the V.22 modem can generate 1,200 bps at 600 baud.)
- Logical name assigned to serial port #1 in DOS and OS/2. COM ports are usually connected to a modem or mouse. DOS version 3.3 or higher supports up to COM4, and OS/2 supports eight COM ports. Also, called RS232 port. See LPT1 port.
RS-232 for Serial Transmission
- A 25-wire electrical interface between a computer and a peripheral device, such as a modem,
a mouse, etc. It is an EIA (Electronic Industries Association) standard for serial transmission that uses a 25-pin DB-25 or a 9-pin DB-9 connector.
Frequency Modulation- A communications transmission technique that modulates a data signal into a fixed carrier frequency by modifying the carrier frequency.
- A simple communications modulation technique that merges binary data into a carrier frequency. It usually creates only two changes in the frequency, one for the 0 bit and another for the 1 bit.
- ?Refers to Quadrature Amplitude Modulation. A modulation technique that generates 4 bits per baud.
- Refers Link Access Procedure Modem. The protocol defined in CCITT V.42. It uses LAPD methods (LAP-D channel) used for the data channel of an ISDN transmission.
- Refers to Microcom Networking Protocol. This is a data compression protocol that has been a standard in the United States. It was developed from microcom, Inc.
Bandwidth
- Refers to transmission capacity of a communications channel. It is the difference between the lowest and highest frequencies transmitted. It is expressed in cycles per second (Hertz).
- Many of these are offered by Intelsat, the International Telecommunications Satellite Consortium, which is owned by 114 governments and forms a worldwide communications system.
- Tips
- In late 1994, RCA introduced a direct broadcast satellite (DBS) system that enables homeowners or businesses to install 18-inch KU-band VSATs to receive satellite broadcasts for about $700. DBS lets owners receive more than 150 TV channels of higher quality video and audio than traditional cable TV. The real potential for DBS lies not only in the replacement of cable TV, but with the coming integration of video, voice, and data, as another high speed circuit into the home and office.
ITU-TSS
- This is an abbreviation of International Telecommunications Union-Telecommunications Standardization Sector.
- It refers Consulative Committee for International Telephony and Telegraphy. CCITT is an international organization for communications standard.
Backbone Networks
- A BN is a large network to which many networks within an organization are connected. It usually is a network that interconnects all networks on a single site, but it can be larger if it connects all the organization's terminals, microcomputers, mainframes, local area networks, and other communication equipment.
Common Carriers
- A common carrier is a government-regulated private company that sells or leases communication services and facilities to the public. A tariff is the schedule of rates and description of services that are to be received when a particular type of communication service is purchased or leased. If the industry is deregulated, as it is in the United States, it may be more innovative, cost effective, and able to develop new services faster.
- These services are leased digital circuits from common carriers with a wide range of transmission capacities.
- SONET (Synchronous Optical Network) has recently been accepted by ANSI as a standard for optical transmission at gigabits per second speeds. It uses fiber optics.
- SMDS (Switched Multimegabit Data Service) offered by most RBOCs (Regional Bell Operating Companies), is essentially a switched version of the T- carrier and SONET services.
- Asynchronous Transfer Mode (ATM) is very similar to frame relay, except that it uses fixed-length packets. ATM is one of the fastest growing new technologies for packet switched networks. ATM is scaleable, and provides forward error correction on the header.
Bitnet
- Bitnet is a worldwide network, separate from the Internet, which connects well over a thousand academic and research institutions in more than 40 countries. Many Bitnet sites are IBM mainframe computers running the VM operating system. Each country has different name for Bitnet.
