Glossary

ADSL - Asymmetric Digital Subscriber Line.

Bandwidth - A measure of the capacity of data that can be moved between two points in a given period of time.

CATV – Cable TV. 

CMTS – Cable Modem Termination System. CMTS is a central device for connecting the cable TV subscribers to the internet. 

CO - Central Office. A telephone company facility where subscribers’ lines are joined to switching equipment for connection to each other, locally and long distance. 

Dial-up Modem - Dial-up modem's connection is just like a regular phone connection, but instead of people, computers are connected to both ends of the connection.
With a dial-up modem, the user must connect to his Internet Service Provider (ISP) in order to connect to the internet.

Downstream - Any data that is moving toward a computer. Data that is being received by a computer is traveling downstream.

Full-Duplex - Sending data in both directions at the same time. Usually higher quality but requires more bandwidth.

Half-Duplex - ending data in both directions, but not at the same time.

ISP - Internet Service Provider is a company that provides Internet access services to consumers and businesses. 

ITU - International Telecommunications Union. A United Nations agency that deals with telecommunications issues. 

Local Loop - The wires that connect an individual subscriber's telephone or data connection to the telephone company central office. 

PAM - Pulse Amplitude Modulation

PCM - Pulse Code Modulation

POTS - Plain Old Telephone Service. POTS is the traditional function of a telephone network to allow voice communication between two people across a distance. 

QAM - Quadrature amplitude modulation

QPSK - Quadrature Phase Shift Keying is a digital modulation technique.

PSTN - Public Switched Telephone Network. PSTN is the regular telephone network or any part of it. Along with telephone services, this network also carries data and other non-telephone services.

Upstream - Any data that is moving away from the computer. Data that is being sent to another machine is traveling upstream.