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The Transmission Infrastructure We pass by transmission on the way to the Intelligent Network (IN) because it is important to understand how all the switching and signalling nodes (not to mention voice links) are connected together. Like the last chapter, we will pass briefly through analogue transmission first as a means of exposing the desires for digital transmission. Then move on to digitisation of speech and look at how large volumes of calls are economically carried across the world. Analogue voice signals can suffer from a number of interference problems ranging from degradation due to distance through to external signalling inducing. | Next Generation Network Services Neill Wilkinson Copyright 2002 John Wiley Sons Ltd ISBNs 0-471-48667-1 Hardback 0-470-84603-8 Electronic 2 The Transmission Infrastructure INTRODUCTION We pass by transmission on the way to the Intelligent Network IN because it is important to understand how all the switching and signalling nodes not to mention voice links are connected together. Like the last chapter we will pass briefly through analogue transmission first as a means of exposing the desires for digital transmission. Then move on to digitisation of speech and look at how large volumes of calls are economically carried across the world. Analogue voice signals can suffer from a number of interference problems ranging from degradation due to distance through to external signalling inducing noise into transmission. One of the big culprits for noise on the line is cross talk. Cross talk occurs when a number of transmission systems are carried through the cabling trunk in close proximity. External noise in the form of interference from electricity mains cabling and other electronic equipment conspire to reduce the speech to an unintelligible hiss. It is this reason as well as economies of scale in amalgamating voice connections together into large transmission systems that has brought about the desire to digitise the analogue signals produced by the human voice. Digital signals are less prone to interference as interference only indirectly affects the signal. The original analogue signal must be decoded from the binary representation as long as the accuracy of the binary representation of the signal is maintained the original signal can be regenerated immune from noise. 20 THE TRANSMISSION INFRASTRUCTURE VOICE DIGITISATION Speech using the handset concept created by Alexander Graham Bell is an analogue signal. It is a continuous signal varying in amplitude and frequency in sympathy with the compression waves created from the human voice box in the process of .

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