COMM 4630 Study Guide - Final Guide: Asteroid Family, Mainframe Computer, Integrated Circuit
Document Summary
Answering a call: the sound wave is converted to electrical signal through a microphone; the electrical current is transformed to sound through the speaker. *tone-the tone key causes a dual frequency signal to be placed on the line, the dual frequencies mix with each other. Bandwidth: sound signal is 4 khz for phone operation; voice signal is 200-3,400khz for phone conversation. Transmission links: metallic, twisted pair, coaxial cable, microwave. Telephone networks: local area network, exchange area network, telecommunications services (wats) and local access transport area (lata) *transmission: pulse code modulation is used to convert analog signal to digital signal; voice signal (4khz) is sampled. Codec: analog-to-digital conversion using pulse code modulation (coder-decoder) Other mobile communication services: improved mobile telephone service, special mobile radio, two- way radio dispatch network, radio paging service (local area network and wide area network services are both available now)
