Carriers and services

Telecommunication carriers provide the telephone lines, satellites, modems and other communications technology used to transmit data from one location to another.

Switched and dedicated lines

• Switched and dedicated lines are standard telephone lines that carriers use to transmit data.
• These lines use switching equipment to allow one transmission device to be connected to other telecommunication devices.

Private branch exchange

• Private branch exchange(PBX) is a communication system that can manage both voice and data within a building and to outside lines.

Digital line subscriber 

• A digital subscriber line(DSL) is a communications line that uses existing phone wires to provide transmission speeds exceeding 500kps (fro 256 kbit/s to 40 Mbit/s)
• it is medium for transferring data over regular phone lines and can be used to connect to the internet.
• A technology that significantly increases the digital capacity of ordinary telephone lines into the home or office.
• DSL speeds are based on the distance between the customer and telecommunication central office.
• ADSL(Asynchronous digital subscriber line)
• A type of combined internet and phone line, it is called asynchronous because the speed of data going out is slower than the data coming in.
• A broadband connection.
• A type of DSL which is a method of transferring data over copper telephone lines.
• An ADSL shares ordinary telephone line by using frequencies above the voice band but the higher inter frequencies interface with regular telephone usage.
• ADSL2
• It adds new features and functionally targeted at improving performance and interoperability and adds support for new applications and services.
• It reduces the initialization time from more than 10 seconds ( as it required for ADSK) to less than 3 seconds
• It has the same signal footprints as ADSL. 

ISDN

• Integrated services digital network (ISDN) is a technology that uses existing common carrier lines to simultaneously transmit voice, video and image data in digital form.
• Use Circuit switching technique
• Package switch
• Circuit Switch

T1 carrier 

• T1 carrier was developed by AT & T to increase the number of voice calls that could be handled through existing cables.
• Use PCM (pulse code modulation) technique.
• A T1 connection has a 1.544Mbps speed developed by 2 dozen 64 kbps channels.