WHAT IS DIGITAL SIGNAL

Digital Signal:
A Signal (Voltage or Current) that can have only two discrete values is called a digital signal.  A square wave is a digital signal because this signal has only two values. +5V and OV and no other value.

WHAT IS ANALOG SIGNAL

Analog Signal:
A continuously varying signal (Voltage or Current) is called an analog signal.  An alternating voltage varying sinusoidally is an analog signal.

WHAT IS DIGITAL CIRCUIT

Digital Circuit:
An electronic circuit that handles only a digital signal is called a digital circuit.

WHAT ARE LOGIC GATES

LOGIC gates:
A digital circuit with one or more input signals but only one output signal is called a logic gate. Logic gate is a switching circuit.

WHAT ARE THREE BASIC LOGIC GATES

Three Basic Logic Gates:
A Logic gate is a circuit that has one or more input signals but only one output signal.  All logic gates can be analysed by constructing a truth table.  A truth table lists all input possibilities and the corresponding output for each input.

The three basic logic gates that make up all digital circuits are 
1) OR gate  2)  AND gate  3) NOT gate  

WHAT IS OR GATE

OR gate:
OR gate has two or more inputs but only one output. The output y of an OR gate is low when all the inputs are low. The output y of an OR gate is High if any or all the inputs are High.

WHAT IS NOT GATE OR INVERTER

NOT gate:
NOT gate or inverter  has only one input and one output, where the output is opposite of the input. The Not gate is also called "inverter" because it inverts the input.

WHAT IS AND GATE

AND gate:
AND gate is a logic gate that has two or more inputs but only one output.  The output y of AND gate is High when all inputs are high.
The output y of AND gate is low if any or all inputs are low. it is also called "all or nothing gate".  Output will be high when both the inputs are high.

NOT GATE FROM NAND GATE

NOT gate from NAND gate:

When two inputs of NAND gate are joined together so that it has one input, the resulting circuit is NOT gate.

NAND Gate is a Universal Gate

NAND gate is a universal gate because its repeated use can produce other logic gates.

WHAT IS NOR GATE

NOR gate:
It is a combination of OR gate and NOT gate.  Output of OR gate is connected to the input of a NOT gate.

WHAT IS NAND GATE

NAND gate:
It is a combination of AND gate and NOT gate.  Output of AND gate is connected to the input of a NOT gate.

WHAT IS DEMORGAN'S THEOREMS

Demorgan's theorems are used in simplifying expressions which includes a product or sum of variables is inverted

Demorgan's First Theorem:

When the OR sum of two variables is inverted, this is equal to inverting each variable individually and then ANDing these inverted variables.

________          ____   _____

A + B    =     A    .  B

Demorgan's Second Theorem:

When the AND product of two variables is inverted, this is equal to inverting each variable individually  and the ORing them.

______    ___       ___

(A . B ) =   A      +  B

WHAT IS ENCODER AND DECODER

Encoder

The Circuit that converts decimal form to digital (binary) form is called Encoder

Decoder

The circuit that converts digital form to decimal form is called decoder

SHORT CUT KEY TO MAXIMISE A WINDOW

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and  type  "ipconfig" and  press "Enter"