Английский язык. Арланова Т.Л - 39 стр.

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39
The input can be any movement or any change in the environment. For
example, a drop in temperature may cause a heating system to come on.
The control may change the size of the output (for example, adjusting the
sound of a TV). Often this involves changing one kind of input into a different
kind of output. For example, opening a window may set off a burglar alarm.
Outputs can be of many kinds. An alarm system may ring a bell, flash
lights, and send a telephone message to the police.
Most control systems are closed loops. That means they incorporate a
way of checking that the output is correct. In other words, they have
feedback. The thermostat in a central heating system (Fig. 2) provides
constant feedback to the control unit.
Temperature
sensor
Control
unit
Boiler
switch
Boiler/Pump
radiators
Feedback
Fig. 2
The control system of modern washing machine has to take into account
several different factors. These are door position, water level, water
temperature, wash and spin times, and drum speeds. Most of them are
dacided when you select which washing program to use.
Fig. 3 shows a block diagram of a washing machine control system. You
can see that this is a complex closed loop system using feedback to keep a
check on water level, water temperature, and drum speeds.
Fig. 3

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