The information revolution: Analogue and digital systems

Analogue and digital systems

In the world of physics, the universe is seen to be made up of energy and matter. These can both be treated in two alternative ways: as waves, or as particles. Light, for example, travels in the form of light waves, but it is also true to say that it travels in the form of particles called photons. We measure waves - their amplitude, and their frequency- but we count particles.

These two quite different ways of dealing with the physical universe apply also to information handling:

• Waves/particles. In the traditional telephone system, for example, the electrical information that carries the speech travels in the form of waves, whereas in modern communications sytems it travels in the form of pulses (of electron particles).

• Measuring/counting. Kitchen scales of the traditional variety measure the weight of food by means of a pointer attached to a spring inside the scale; electronic scales, in contrast, carry out the task by counting, displaying the result on a digital readout. Traditional watches use a system of gears to measure the passage of time, whereas digital watches work by counting the oscillations of a quartz crystal.

We could give many other examples contrasting these two kinds of information-handling devices. The first type of device is referred to as analogue, the second as digital (since it is based on counting numerical digits). One of the major effects of the information revolution has been to replace our many analogue systems with digital ones. So we hear much today of the new digital audio systems, digital TV, digital communications systems, and so on.

There are two main reasons for this change:

1 Microchips, and therefore the devices that incorporate them, handle information in digital form. (See Chapter 2 for detail on this.) If you want to use computers to aid the production of music, for example, you must first convert the sound waves to digital electrical pulses in a Wire.

2 Digital information can be stored and communicated without any degradation, whereas analogue information degrades. This degradation is very apparent when you make several generations of copies of an audio tape. Eventually, the quality becomes so poor that the copy is worthless. Compare this to information in digital form, for example data stored on a computer disk. You can make as many generations of copy as you like, and the final disk is still identical to the original.

The information in the case of the computer disk is stored as a series of magnetized spots on the disk. A particular location is either magnetized (representing the digit 1) or not magnetized (representing the digit 0). When you copy a disk, an identical series of 1s and Os is produced on the copy - there is no possibility of a '1' being degraded to 0.99, as you would get in an analogue system. And although it is theoretically possible for a '1' to be copied to a '0' in error, various checking techniques can be applied to ensure that this does not happen.

(In the case of communications systems, digital data will degrade if the signal travels for a long distance without boosting. In this case the message may be completely scrambled - an effect that is sometimes observed with Ceefax or Oracle pages.) Digital systems, then, offer the twin advantages of com­puter control and high quality. That's why audio, video, communications, and other systems are all going digital. An important by-product is that all forms of information, whether image, sound, or data, can be handled by the same equipment.

Systems theory

The information revolution has not only changed the way we live and the technology we use, it has also altered the way we think. Words such as 'input' and 'output', part of our everyday language now, are evidence of this. Increas­ingly, we think in a 'systems' way.

Systems theory - or cybernetics - was developed to provide a conceptual approach to modem engineering and IT systems. It has permeated much of our thinking, and is now applied to other types of system, such as biological systems and social systems. Like all good theories, the underlying idea is simple and elegant. A device such as a computer, or a social organization such as a business, or a living creature such as a human being, can be viewed as a 'black box' which converts inputs received from its environment to outputs transmitted to its environment. Control is exercised, not by monitoring what goes on inside the black box, but by monitoring the outputs that emerge from it, and adjusting the inputs in the event of undesirable output variations (see Figure 1.2).

To illustrate this, think about a simple engmeenng system, a central heating system:

• The 'black box' is the boiler and pump which heats the water and pumps it around the system.

• The inputs it receives from its environment are the gas and electricity needed to run the boiler and pump.

• The output to its environment is the heat released by the radiators into the rooms.

• Control is exercised by the thermostat, which monitors the heat in the room, and adjusts the inputs (i.e. switches the boiler on or off) if the heat falls below or rises above the required temperature range.

These same concepts can be applied to the way in which a department of a business is run. In this case the department is the 'black box', the inputs are the staff, the equipment and materials, and so on, and the outputs are what the department produces. In control of the department is a manager. If he (or she) manages in the traditional way, using non-systems thinking, he will exercise control by keeping a watchful eye on the way in which his staff work, ensuring that they have their heads down, conform to the laid-down procedures, and so on.

The more up-to-date systems approach to control is to set the department's output targets, and then let the staff get on with the job. The manager is not concerned with how the 'black box' works - how the targets are met is up to the staff- the manager needs to take action only if the targets are not met. This action will involve adjusting the inputs, e.g. strengthening the staff by giving more training or improving the equipment.

It is clear that the systems approach needs careful plan­ning of output targets, as these must be realistic. It also means setting up procedures to allow the manager to monitor the output by producing feedback on the work of the section in the form of reports (see below). The benefits gained, though, are greater efficiency and motivation as well as a reduced need for management to control the minutiae of the business's operations.

Turning now to the business as a whole, this too can be regarded as a system under the control of the board of directors or top management. Control is exercised by com­ paring the profit generated by the business (its main output) against the level of profit anticipated by the business plan, and issuing from time to time short-term budgets to keep the business on course (see Figure 1.3). The feedback reports used by top management to control the business will include profit and loss reports, sales reports, and other measures of overall business performance.