ISYS111 Lecture 3: ISYS111 WEEK 3
12 Jan 2019
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Document Summary
A system that connects computers and other devices via communications media so that data and information can be transmitted among them. A firewall is a software program or piece of hardware that helps screen out hackers, viruses, and worms that try to reach your computer over the internet. Lan local area network connects communications devices in a limited geographical area such as a building. Wan wide area network covers a wider geographical area. Analogue vs. digital signals: analogue signal: continuous waves. Frequency: pitch: digital signal: discrete pulses. On or off (1 or 0: modem (modulator demodulator) Converts digital signals to analogue and vice versa. Types: dial-up modem, cable modem, digital subscriber line (dsl) modem. Communication media and channels: transmission speed bps, hertz, bandwidth, cable twisted wire lan cabling: cat5 (rj45) coaxial cable fiber optics, broadcast microwave satellite radio infrared. A network protocol defines rules and conventions for communication between network devices.
