Development of the Phone System

A good example of engineering design is the telephone system. Long and meticulous research was conducted at Bell Laboratories on human perception of speech. This created the specification for the required bandwidth and noise level for speech intelligibility. Engineers perfected the microphone that would translate the pressure waves into electrical waves to meet the specification. Then these electrical waves were transmitted through copper wires over long distances to a similar device, still preserving the required specification. For increased functionality the freedom of reaching any other telephone was added to the system, so switching of calls had to be implemented. This created the phone system. Initially, the switching among lines was done by operators. Then a machine was invented that would automatically switch the calls. Operators were still used for special services such as directory assistance, but now that the fundamental engineering aspects are stable, we are asking machines to automatically recognize speech and directly assist callers.

The development of the phone system is an excellent example of engineering design. Once we have a vision, we try to understand the principles at work and create specifications and a system architecture. The fundamental principles at work are found by applying the scientific method. The phenomenon under analysis is first studied with physics or mathematics. The importance of models is that they translate general principles, and through deduction we can apply them to particular cases like the ones we are interested in. These disciplines create approximate models of the external world using the principle of divide and conquer. First the problem is divided in manageable pieces, each is studied independently of the others, and protocols among the pieces are drawn such that the system can work as a whole, meeting the specifications drawn a priori. This is what engineering design is today.

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