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## 'Circuit Maker' printed from http://nrich.maths.org/

A circuit is a set of switches, wires, bulbs and components called

logic gates .

There are seven different types of logic gates, each with a
technical-sounding name:

AND

OR

XOR (exclusively OR)

NAND (not AND)

NOR (not OR)

XNOR (not XOR)

NOT

One wire comes out of each logic gate and in the examples below
this wire is always attached to a bulb. The bulb is on or off
depending on the inputs from the switches and the type of logic
gate.

Here is a circuit containing one of each type of gate wired up to a
bulb.

By clicking the switches on or off (using the blue square in their
top left hand corners), can you work out what each of the different
logic gates does?

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Now that you are familiar with the properties of the gates you can
experiment by building your own circuits with interesting
properties using the interactivity below. Instructions are given at
the bottom of the page. You can find some ideas and challenges in

Simple
Counting Machine
You can also read and learn more about logic circuits and gates and
mathematical logic in the article

Logic, Truth Tables and Switching Circuits
.
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INSTRUCTIONS

To build a circuit follow these steps. You can delete mistakes by
clicking on the cross which appears when you hover above the
icon.

1. Left-click on the components to drag them on to the circuit
board space.

2. FIRST click next to a red dot and drag to the right to create a
wire; THEN you can stretch this wire to join with any other red dot
in the circuit.

3. Click on the switches to turn them on or off. Wires 'fill' with
current unless blocked by an un-triggered logic gate.

4. Click on the logic gates to change their type.

5. Left-click and drag to move the components around.

The key ideas are shown in this picture; by clicking on the
triangle you can also watch a short video clip (1Mb) of the
creation of the circuit.

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