1. Communications 14.2 Digital Signals

2. 14.1 Solve problems involving the conversation between binary numbers and decimal numbers Power of 23210 8421 Eightsfourstwosones 2^32^22^12^0 Power of 103210 1000100101 thousandshundredsTensUnits 10^310^210^110^0

3. Convert the following binary numbers into base 10 (to decimal numbers) 1001011 (2) =(2^6)+(2^3)+2+1 =64+8+2+1=75

4. Decimal  binary numbers 14 =(8+4+2) =2^3+2^2+2^1 =1110(2)

5. 14.2 Distinguish between analogue and digital signals 有 Continuous variation  analogue Signals continuously changing from one amplitude to another Continuous variation X …either high or low  digital

6. 14.3 State the advantages of the digital transmission, as compared to the analogue transmission, of information Noise= when affected by noise, information is unaltered Source independence= independent of what type of into is transmitted…speech text video all in same signal Bandwidth & Compression= compressing does not change the info just enables it to transmit quickly Transmission rate, multiplexing, coding, data manipulation

7. 14.4 Describe, using block diagrams, the principles of the transmission and reception of digital signals Sample and hold clock ADC Analogue to digital converter Analogue data Parallel to serial converter modulator Carrier wave transmission Sample data converted into “bytes” Provides the reference pulses Converts bytes to pulses

8. 14.5 Explain the significance of the number of bits and the bit-rate on the production of a transmitted signal Number of bits transmitted per second  bit rate=data transfer rate Bit rate= number of bits per sample * sampling frequency Greater the bit rate, higher the quality of the reproduced transmitted data

9. Nyquist theorem=sampling theory To ensure accurate reproduction of the signal must be equal to, or greater than twice the signal frequency

10. 14.6 Describe what is meant by time- division multiplexing Time division multiplexing

12. 14.7 Solve problems involving analogue-to-digital conversion Pg 400

13. 14.8Describe the consequences of digital commutation and multiplexing on worldwide commutations The amount of information and the speed with which it now can be transmitted across the world…very very fast

14. 14.9 Discuss thee moral, ethical, economic and environmental issues from access to the internet Can spread political or religious propaganda Illegal goods sold Pornography for minors ‘internet shopping’ and its effect economically and socially World’s energy consumption