This is a foundation course on telecommunication and related technologies. It describes the essential elements of a modern communication system. Students will learn the basic concepts in electrical communication, the operation principles and the performance requirements for a real-world communication system. The course content include signal representation and properties, amplitude modulation, angle modulation, analogue-to-digital signal conversion, demodulation and detection, pulse modulation, multiplexing, baseband transmission, passband transmission, inter-symbol interference, system performance evaluation and other topics. The course is the basis of various advanced courses on electrical and optical communications.