 signal is very good or excellent. 3. Why do we use a sinusoidal test tone when we measure S/N on a speech channel rather than just the speech signal itself? 4. The noise level of a certain voice channel is measured at -39 dBm, and the test-tone signal level is measured at +3 dBm. What is the channel S/N? 5. If we know the loudness rating of a telephone subset earpiece and of the subset mouthpiece, what additional data do we need to determine the overall loudness rating (OLR) of a telephone connection? The BER of an underlying digital circuit is 1 X 10-8. for data riding on this circuit. What is the best BER we can expect on the data? 7. What are the three basic impairments on a telecommunication transmission channel? 8. Of the three impairments, which one affects data error rate the most and thus limits bit rate? 9. Explain the cause of phase distortion. 10. Name the four types of noise we are likely to encounter in a telecommunica- tion system. 11. What will be the thermal noise level of a receiver with a noise figure of 3 dB and a bandwidth of 1 MHz? 12. Define third-order products based on the mixing of two frequencies F1 and F2. 13. Give four causes of impulse noise. REFERENCES 14. Relate VU to dBm for a simple sinusoidal signal. Relate VU to dBm for a complex signal such as human voice. 15. Echo as an annoyance to a telephone listener varies with two typical causes. What are they? What is the most important (most annoying)? REFERENCES 1. Effect of Transmission Impairments, ITU-T Rec. P.11, ITU Helsinki, Mar. 1993. 2. Loudness Ratings on National Systems, ITU-T Rec. G.121, ITU Helsinki, Mar, 1993. 3. R. L. Freeman, Telecommunication System Engineering, 4th ed., Wiley, New York, 2004. 4. R. L. Freeman, Telecommunication Transmission Handbook, 4th ed., Wiley, New York, 1998. TRANSMISSION AND SWITCHING: CORNERSTONES OF A NETWORK TRANSMISSION AND SWITCHING DEFINED The IEEE defines transmission as the propagation of a signal, message, or other form of intelligence by any means such as optical fiber, wire, or visu