Chapter 8 Telecommunictions

Microwaves

-Microwaves are radio waves that provide a high-speed signal transmission. -Often called fixed wireless, involves sending signals from one microwaves station to another.

Modems

-Some mobile users have a wireless modem uses the mobile service provider's network to connect to the Internet wirelessly from a computer or mobile devices. -Wireless modem have external or build-in antenna, are available as USB flash drive. -Some smartphones function as a wireless modem, called a mobile hot spot.

Servers

-Sometimes called a host computer. -It control access to the hardware, software and other resources on the network and provided a centralized storage area for program, data and information.

Wireless Access Points

-(WAP) is a central communications device that allows computers and devices to transfer data wirelessly among themselves or to a wired network. -It has high quality antennas for optimal signals and suggest positioning at the highest possible locations.

Dedicated Lines

-A dedicated line is a type of always-on connections that uses analog or digital lines. -A dedicated line are better than dial up because dedicated lines provides a constant connection. Five type of dedicated line -ISDN lines, DSL, FTTP, T-carrier lines and ATM

Modems (Dial up Modems)

-A dial up modem converts signals between analog and digital, so that data can travel along an analog telephone line. Usually is in the form of adapter card.

Dial-up Lines

-A dial-up line is a temporary connection that uses analog telephone lines for communications.

Hubs and Switches

-A hubs / switch is a device that provides a central point for cable in a network. -Larger networks typically use a hub, while smaller networks use a switch -Some H&S include router. The H&S receives data from many directions and then forward it to one or more destinations.

Routers

-A router connects multiple computers or other routers together and transmits data to its correct destination on a network. Example: -Home network: router allows multiple computers to share a single high speed Internet connection such as through a cable modem/DSL modem. -To prevent unauthorized users form accessing files and computer, many are protected by a build-in firewall.

ADSL

-ADSL connections transmit data downstream (receiving) at a much faster rate than upstream (sending).

Broadcast Radio

-Broadcast radio is a wireless transmission medium that distributes radio signals through the air over a long distances. Example: -Bluetooth

Cellular Radio

-Cellular radio is a form of broadcast radio that is used widely for mobile communications specifically wireless modems and mobile phones.

DSL

-Digital Subscriber Line (DSL) transmit at fast speeds on standard telephone lines with both voice and data communications. -Asymmetric DSL (ADSL) is a type of DSL that supports faster transfer rates when receiving data(downloading) than when sending data(upload).

Introduction to basic components

-Digital communications describes a process in which two or more computers or devices transfer data, instructions, and information. -Successful communication in the following 1. Sending device - Transmission media - Receiving device

FTTP

-Fiber to the premises (FTTP) uses fiber-optic cable to provide extremely high-speed Internet access.

Fiber-Optic Cable

-Fiber-Optic Cable consists of strands of glass (called optical fibers) that use light to transmit signals.

ISDN Lines

-Integrated Services Digital Network (ISDN) is a set of standards for digital transmission of data over standard telephone lines.

Communication Channel

-Is the transmission media on which data, instructions or information travel in a communications system. Common terms: -The amount of data that can travel over a communications channel. -Latency is the time it takes a signal to travel from one location to another network. -Transmission media consists of materials capable of carrying one or more signals. -Broadband media transmit multiple signals simultaneously.

Coaxial Cable

-It consists of a signal copper wire surrounded by three layer: -insulating material -woven or braided metal -plastic outer coating Example: -Cable television network wiring

Communications Satellite

-It is a space station that receives microwaves signals from an earth-based station, amplifies it and broadcast the signal over a wide area.

Network Cards

-Sometimes called a network interface card (NIC) enables a computer or device that does not have build in networking capability to access a network. Available variety of styles -Desktop computer is an adapter card that has a port to which a cable connects. -Mobile computer: USB network adapter, Express Card module or PC card.

T-Carrier Lines

-T-Carrier Lines is a long-distance digital telephone line that carry multiple signals over a single communications line.

Communications Over the telephone network

-The public switched telephone network (PSTN) is the worldwide telephone system that handles voice oriented telephone calls. -The telephone network is an integral part of computer communication. -Data, instructions and information are transmitted over the telephone network using dial up lines or dedicated lines.

Twisted-Pair Cable

-Widely used in network cabling and telephone system. -Twisted-pair cable consists of one or more twisted-pair wires bundled together. -Each twister pair wire consists of two separate insulated copper wires that are twisted together. -The wires are twisted together to reduce noise. Noise is an electrical disturbance that can degrade communications.

Introduction to basic components

1. A sending device initiates an instruction to transmit data, instructions or information. 2. A transmission media or communication channel is the medium on which the data, instructions or information level. 3. A communication device is a hardware that connects the sending device to transmission media , and connects the transmission media to receiving device. 4. A receiving device accepts the transmission of data, instruction or i information.

Types of lines

1. Dial-up lines 2. Dedicated line 3. ISDN line 4. DSL 5. FTTP 6. T-carrier line 7. ATM

Two type transmission media

1. Physical transmission media -Use wire, cable and other tangible materials to send communications signal. Example: -Twisted pair cable -Coaxial cable -Fiber optic cable 2. Wireless transmission media -Send communications signals through the air or space using radio, microwave and infrared signal.

Advantages and Disadvantages of Fiber-Optic Cable

Advantages: -Carry more signals than wire cables -Faster data transmission -Less susceptible to noise, hence better security -Smaller size (much thinner and lighter weight) Disadvantages: -Costs more than twisted-pair and coaxial cable -Difficult to install and modify

ATM

Asynchronous Transfer Mode (ATM) is a service that carries voice, data, video and multimedia at very high speeds.

Physical components of a network

Example -Modem, Network card, wireless access point, routers, hubs and switches

-One type of communication device that connects a communications channel to a sending or receiving device is a MODEM. -Function MODEM is to convert digital signals to analog signal and analog to digital. Types of MODEM: -Dial up Modems -Digital modem -Wireless modem

Modems

Infrared

·Infrared (IR) is a wireless transmission medium that sends signals using infrared light waves. -Communicate over short distance -Use in mouse, printers, digital cameras and hand phone.