Modems Flashcards
What does modem stand for ?
Modulator demodulator
What is a modem used for ?
To convert analogue into digital.
Two types of modems they are ?
Serials modems and parallel modems.
What is a serial modem ?
A serial modem transmits and receives one bit of data at a time
What is a parallel modem ?
A parallel modem transmits and receives data on a number of levels at the same time.
What are he advantages of serial modems ?
Reduction of cable size (less expensive )
No requirement for synchronisation
Disadavantges of serial modems?
Slower transmission times
Advantages of parallel modems ?
Can send a bulk of data compared to serial modems.
Disadvantages of parallel modems ?
Requires an internal clock to maintain synchronicity
Requires a signalling command to transmit data
Where are modems employed?
Used to convey digital data between transmit and receive terminals
What are the 5 types of modems ?
Narrowband/phone dial up, radio modems, wifi/WiMAX, mobile and router modems and broadband.
What are the two modes that a narrowband modem can be in ?
Data mode and command mode.
Where are radio modems usually employed ?
They are employed for use in high speed computer network links where laying cables would be uneconomical.
Wireless data modems where are they used ?
Wifi and WiMAX.
What advantages does WiMAX have over wifi?
Faster speeds at greater distances.
What does WiMAX stand for ?
World wide interoperability for microwave access.
Examples of mobile modems and routers?
Umts universal telecommunications systems
hspa high speed packet access
gprs general packet radio service.
3 Examples of new cellular modem technologies ?
Umts hspa and WiMAX
What are broadband modems ?
It is a modem that is capable of modulating/demodulation 100s of channels simultaneously.
What does ITU stand for ?
International telecommunications union
What is the ITU?
An agency of the United Nations which regulates information and communication technology issues
What are the 4 sectors within ITU?
ITU-R radio communication
ITU-T standardisation
ITU/D the development sector
ITU-TV recommendations for modems and data over telephone.
What types of data can be sent over modems ?
Digital facsimile, high speed data, telemetry and high speed control.
