Async, Sync And Line Coding

Question 1

Define asynchronous systems ?

Answer 1

It is an encoding technique to maintain synchronicity between transmission systems. They do not require any linked timing devices.

Question 2

Define synchronous systems ?

Answer 2

It is an encoding technique to maintain synchronicity between transmission systems. It requires clocking devices at both transmit and receiver systems. ( must be synchronised )

Question 3

There are two common types of systems that maintain synchronicity they are ?

Answer 3

Async and sync

Question 4

Once asynchronous system is running from where does the receive terminal clock take its timing source from ?

Answer 4

It takes its timing from the centre of each bit if the transmit and receive terminal clocks are running at the same speed

Question 5

How often is asynchronous system clock resynced?

Answer 5

On completion of each frame the clock will resync

Question 6

Determine the overhead of an asynchronous system whose complete frame consists of one start bit 19 data bits and 2 stop bits. Answer to 1 decimal place,

Answer 6

3/21= 0.1

Question 7

Why are asynchronous systems generally limited to a maximum amount of data they are able to send between start and stop bits ?

Answer 7

More prone to a timing error and drift could occur

Question 8

What percentage overhead does an asynchronous system generally employ?

Answer 8

40%

Question 9

State two methods that a synchronous system may utilise to be able to achieve timing synchronisation between transmit and receive terminals?

Answer 9

Character oriented transmission and bit oriented transmission

Question 10

In character oriented synchronous system what three elements make up the total frame structure?

Answer 10

Sun characters, control characters and data characters.

Question 11

What additional synchronisation allows a receive terminal of a synchronous system to determine the beginning and end of a frame of data ?

Answer 11

Pre amble and post amble bit pattern

Question 12

Typically what is the general size in bits of the control information within a synchronous system system ?

Answer 12

8 bits

Question 13

What does a synchronous system frame consist of ?

Answer 13

…

Question 14

What is encoding ?

Answer 14

To ensure the maximum amount of data stream is received with minimal errors at the receive terminal.

Question 15

Describe in detail a character oriented transmission scheme ?

Answer 15

Syn character| control character| data character|control characters.