Digital communication

http://www.moneysupermarket.com/broadband/adsl/

http://www.broadband-guide.org.uk/what-is-broadband.html

http://en.wikipedia.org/wiki/Short_Message_Service#Technical_details

http://cellphones.about.com/od/phoneglossary/g/mmspicturemessaging.htm

http://en.wikipedia.org/wiki/Broadband#In_telecommunication

http://en.wikipedia.org/wiki/ADSL

http://www.w3schools.com/tcpip/tcpip_intro.asp

http://wiki.answers.com/Q/How_does_Bluetooth_work