1. Principles of Signal Theory
BTEC National

2. Signal Theory
Data is represented in digital format based on binary (base 2) principles
Digital signals are discrete.

3. Data The smallest element of data is the ‘bit’ or ‘binary digit.’
This can be represented by a ‘0’ or a ‘1’.
When bits are grouped together they can be more useful units of data. For example 8 bits form a byte

4. Converting Denary to Binary
To convert denary to binary you must firstly know the ‘base 2’ rules. (This is similar to the units, tens, hundreds you were taught at primary school)

5. Converting Denary to Binary
= 47
We work this out by looking at the headings
And adding the numbers up.
= = 47. Therefore 47 is represented as (byte format)

6. Concept of a packet
In networking, data must be formed in a suitable ‘package’ to be able to be transported across the network.
The actual format of the package is different for different types of network. However the term ‘data packet’ is always used to describe the package

7. Concept of a packet
A data packet should minimally contain the source and destination address, data and error control.
Source Address
Destination Address
Data
Error Control
The source address is sent so the recipient knows who has sent the data. The destination address is used to find the right recipient. Data is the ‘actual message’. Error control is sent to help identify problems with the data once it has been received.

8. Asynchronous versus synchronous transmission
Asynchronous transmission means that device 2 (the receiver) must acknowledge receipt of the data before device 1 (the sender) will send more.
In synchronous transmission both devices (sender and receiver) will synchronise with each other before the data is sent.

9. Bandwidth
This is generally defined as the quantity of data that can be sent through data transmission over a specified period of time.
Bandwidth is usually quoted in (from slow to fast)
Bits per second (bps)
Kilo bits per second (kbps)
Mega bits per second (mbps)
Giga bits per second (gbps)