GCSE Additional Applied Science Jan 2008 Communications Paper B

GENERAL CERTIFICATE OF SECONDARY EDUCATION A326/02 TWENTY FIRST CENTURY SCIENCE ADDITIONAL APPLIED SCIENCE A Communications (Higher Tier) FRIDAY 25 JANUARY 2008 Morning Time: 45 minutes Candidates answer on the question paper. Additional materials: Calculator Pencil Ruler (cm/mm) H * C U P /T 4 7 8 0 3 * This document consists of 11 printed pages and 1 blank page. SP (MML 15405 1/07) T47803/3 © OCR 2008 [A/103/3783] OCR is an exempt Charity [Turn over INSTRUCTIONS TO CANDIDATES • Write your name in capital letters, your Centre Number and Candidate Number in the boxes above. • Use blue or black ink. Pencil may be used for graphs and diagrams only. • Read each question carefully and make sure that you know what you have to do before starting your answer. • Answer all the questions. • Do not write in the bar codes. • Do not write outside the box bordering each page. • Write your answer to each question in the space provided. INFORMATION FOR CANDIDATES • The number of marks for each question is given in brackets [ ] at the end of each question or part question. • The total number of marks for this paper is 36. FOR EXAMINER’S USE Qu. Max. Mark 1 5 2 10 3 8 4 7 5 6 TOTAL 362 © OCR 2008 Answer all the questions. 1 This question is about how a company determines product specifications. Cambridge Radio Solutions is designing a new two-way radio system for use on farms. (a) They start to fill in a specification for the new two-way radio system. key factor notes cost must be cheaper to use than mobile phones network coverage use citizen band frequencies to avoid need for a licence Write in three more key factors, with notes to justify them. [3]3 [Turn over © OCR 2008 (b) The design team at Cambridge Radio Solutions discuss some wider aspects of the product specification. One aspect they consider is their profit margin. This is how much money they need to make on each two-way radio system that they sell. Suggest and justify two other wider aspects of the product specification that they should consider. wider aspect notes profit margin we must make money on each system or we’ll go bust [2] [Total: 5]4 © OCR 2008 2 Here is the circuit diagram of a simple message system. 6.0 V 1.8 V, 0.25 A (a) When the LED is operating, its voltage and current are 1.8 V and 0.25 A. (i) Draw a voltmeter connected to measure the voltage across the LED. [2] (ii) Calculate the power of the LED when the switch is closed. Use P = VI. power = ..................................................... W [2] (iii) Explain how the resistor protects the LED in the circuit. .......................................................................................................................................... .......................................................................................................................................... .................................................................................................................................... [2]5 [Turn over © OCR 2008 (b) Here is an incomplete block diagram for the simple message system shown on the previous page. copper wire link output input (i) Complete the diagram by putting the names of the components in the input and output blocks. [2] (ii) What does the block diagram show? .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .................................................................................................................................... [2] [Total: 10]6 © OCR 2008 3 Here is an incomplete block diagram for a radio receiver. (a) Complete the diagram by entering these words into the boxes. aerial amplifier demodulator loudspeaker tuner [3] (b) Here is the block diagram of the radio transmitter. power amplifier modulator oscillator aerial microphone The transmitter uses frequency modulation. Describe the process of frequency modulation. You may draw diagrams of the signals to help your answer. ......................................................................... ......................................................................... ......................................................................... ......................................................................... ......................................................................... ......................................................................... ......................................................................... ......................................................................... .........................................................................7 [Turn over © OCR 2008 ......................................................................... ......................................................................... ......................................................................... ......................................................................... ......................................................................... ......................................................................... ......................................................................... ......................................................................... ................................................................... [3] (c) The bandwidth of frequency modulated radio broadcasts in the VHF band is 100 kHz. (i) What does bandwidth mean? .......................................................................................................................................... .................................................................................................................................... [1] (ii) State a frequency for radio broadcasts in the VHF band. frequency = ................................................ MHz [1] [Total: 8]8 © OCR 2008 4 Sign language uses a visual code to communicate with deaf people. Here is the code for the letter E. E (a) Name a code which uses digital electrical signals to communicate messages. ................................................. code [1] (b) Sign language uses an analogue code. A digital code would have a lower error rate but also a lower data transmission rate. The range would remain unchanged. What is meant by the terms in bold? error rate .................................................................................................................................. .................................................................................................................................................. data transmission rate .............................................................................................................. .................................................................................................................................................. range ........................................................................................................................................ ............................................................................................................................................ [3]9 [Turn over © OCR 2008 (c) Video uses electrical signals in wires to send pictures. Draw a block diagram for a simple video system. Describe the function of each block. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. ............................................................................................................................................ [3] [Total: 7]10 © OCR 2008 5 Digital signals can be used to carry information about pictures. © iStockphoto.com/Kelvin Wakefield (a) The picture is displayed on a computer screen. Complete the sentences. Choose words from the list. circles frame pixels rows screen window The whole picture is called a ………………………… . It is made of ………………………… which are arranged in ………………………… . [3] (b) A single picture on the screen requires 42 000 bytes of information. (i) Calculate the number of bits of information for a single picture. bits per picture = .......................................................... [1] (ii) The video signal to the screen has a bit rate of 6 720 000 bits per second. Calculate the refresh rate for the screen. refresh rate = ......................... pictures per second [2] [Total: 6] END OF QUESTION PAPER11 © OCR 2008 BLANK PAGE PLEASE DO NOT WRITE ON THIS PAGE12 © OCR 2008 PLEASE DO NOT WRITE ON THIS PAGE Copyright Acknowledgements: Q.5 image © iStockphoto.com/Kelvin Wakefield Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (OCR) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. OCR is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.