1. Analogue an Digital Signals 01001011010011001001010010010010

3. Analogue TV

4. How are digital television pictures sent? The TV program is filmed, This is a real life analogue signal It is converted to a Digital signal The signal is transmitted using radio waves It is received by your aerial and decoded at your house Watch TV

5. Make your own signal 0 = 0 1 = 1 2 = 10 3 = 11 4 = 100 5 = 101 6 = 110 7 = 111 8 = 1000 9 = 1001 10 = 1010 7 111 110

6. 1 Sec Sampled at 2 Hz Signal Consisting of 1 Hz, 5 Hz and 10Hz

7. 1 Sec Sampled at 5 Hz Signal Consisting of 1 Hz, 5 Hz and 10Hz Here we seem to obtain a good sin wave at a frequency which was not present in the original signal. This is called ‘Aliasing’.

8. 1 Sec Sampled at 10 Hz Signal Consisting of 1 Hz, 5 Hz and 10Hz

9. 1 Sec Sampled at 20 Hz Signal Consisting of 1 Hz, 5 Hz and 10Hz

10. Sampled at 40 Hz Signal Consisting of 1 Hz, 5 Hz and 10Hz 1 Sec

11. A Noise Signal

12. Analog Signal with Noise (Large Signal to Noise Ratio)

13. Analog Signal with medium Signal to Noise Ratio The signal can be recovered reasonably well by smoothing (but each time we do this the corruption is increased.)

14. Analog Signal with small signal to noise Ratio Even if we try to recover the signal by smoothing it is corrupted.

15. Digital Signal

16. Digital Signal Signal with quite large signal to noise ratio. The signal only consists of ‘1’s and ‘0’s so it can be recovered exactly. This can be done as many times as necessary.

17. The advantages of digital signals The disadvantages of digital In pairs discuss Unwanted noise quality Quantity of information Unwanted errors Easy to use The advantages of analogue signals The disadvantages of analogue simple complicated Needs extra equipment Difficult for humans to understand Easy for computers to work with

18. Write your own code and swap with your neighbour to decode A 0 B 1 C 10 D 11 E 100 F 101 G 110 H 111 I 1000 J 1001 K 1010 L 1011 M 1100 N 1101 O 1110 P 1111 Q 10000 R 10001 S 10010 T 10011 U 10100 V 10101 W 10110 X 10111 Y 11000 Z 11001 Put commas between the words to help the decoding Encoding