Lesson 6 Basic Signal and Number Systems

What are the two distinct states represented by digital signals?

• All of the above

• On/Off

• True/False

• High/Low

Which type of signal represents continuous ranges of values?

• Binary

• Analog

• Digital

• Hexadecimal

Answer explanation

Analog signals represent continuous ranges of values, unlike binary and digital signals, which are discrete. Hexadecimal is a numeral system, not a signal type. Therefore, the correct answer is Analog.

What is the base of the binary number system?

• 16

• 2

• 8

• 10

Answer explanation

The binary number system is based on two digits: 0 and 1. Therefore, its base is 2, making it distinct from other systems like decimal (base 10) or hexadecimal (base 16).

Which of the following is an example of a digital input?

• Push button

• Relay contacts

• Temperature sensor

• Proportional valve

Answer explanation

A push button is a digital input because it provides a binary signal (on/off) when pressed. In contrast, relay contacts, temperature sensors, and proportional valves are not classified as digital inputs.

What does the term 'ADC' stand for in the context of PLCs?

• Analog Digital Code

• Automatic Data Collection

• Analog Data Control

• Analog to Digital Converter

Answer explanation

In the context of PLCs, 'ADC' stands for 'Analog to Digital Converter'. This device converts analog signals into digital data, which is essential for processing in PLC systems.

Which number system uses 16 digits including A to F?

• Hexadecimal

• Decimal

• Binary

• Octal

Answer explanation

The hexadecimal number system uses 16 digits: 0-9 and A-F, where A represents 10, B represents 11, and so on, up to F which represents 15. This distinguishes it from decimal (10 digits), binary (2 digits), and octal (8 digits).

What is the primary purpose of a parity bit?

• To encrypt data

• To convert data types

• To check data accuracy

• To increase data size

Answer explanation

The primary purpose of a parity bit is to check data accuracy. It adds an extra bit to a binary number to ensure that the total number of 1s is even or odd, helping to detect errors in data transmission.

In the context of PLCs, what does BCD stand for?

• Binary Coded Decimal

• Base Coded Decimal

• Binary Communication Data

• Binary Control Data

Answer explanation

In PLCs, BCD stands for Binary Coded Decimal, which is a way to represent decimal numbers in binary form. Each digit of a decimal number is represented by its own binary sequence, making it easier for digital systems to process.

Which of the following is NOT a characteristic of digital signals?

• Easy to process

• Simple and reliable

• Continuous range of values

• Fast response time

Answer explanation

Digital signals are characterized by discrete values, not a continuous range. They are easy to process, simple, reliable, and have fast response times, making 'Continuous range of values' the correct choice as it does not apply.

What is the main advantage of using Gray code?

• Faster processing speed

• Higher data capacity

• Error minimizing code

• More complex representation

Answer explanation

The main advantage of Gray code is that it minimizes errors during transitions between values. Only one bit changes at a time, reducing the chance of misreading values, making it ideal for applications like rotary encoders.