an blame on the hybrid. What are they? 33. What is the balance return loss on a particular hybrid connectivity when the bal- ancing network is set for a 900-S loop, and this particular loop has only a 300-S impedance? 34. What are the two generic methods of multiplexing? A mixer used in an FDM configuration has a local oscillator frequency of 64 kHz and is based on the CCITT modulation plan. After mixing (and filtering), what is the resulting extension of the desired frequency band (actual frequency) limits at 3 dB points)? 36. The standard CCITT supergroup consists of groups and occupies the frequency kHz to kHz? How many standard voice channels does it contain? 37. What are pilot tones and what are their purpose in an FDM link? REFERENCES 1. R. L. Freeman, Telecommunication System Engineering, 4th ed., Wiley, New York, 2004. 2. R. A. Mina, "The Theory and Reality of Teletraffic Engineering," Telephony article series, Tele- phony, Chicago, 1971. 3. R. L. Freeman, Reference Manual for Telecommunication Engineering, 3rd ed., Section 1, Wiley, New York, 1994. 4. Transmission Systems for Communications, 5th ed., Bell Telephone Laboratories, Holmdel, NJ, 2002. 5. W. D. Reeve, Subscriber Loop Signaling and Transmission Handbook-Analog, IEEE Press, New York, 1992. 6. Recommendations Concerning Translating Equipments, CCITT Rec. G.233, Geneva, 1982. 7. R. L. Freeman, Telecommunication Transmission Handbook, 4th ed., Wiley, New York, 1998. TRANSMISSION ASPECTS OF VOICE TELEPHONY 5.1 CHAPTER OBJECTIVE The goal of this chapter is to provide the reader with a firm foundation of the analog voice channel. Obviously, from the term, we are dealing with the transmission of the human voice. Voice is a sound signal. That sound is converted to an electrical signal by the mouthpiece of the subscriber subset. The electrical signal traverses down a subscriber loop to a local serving switch or to a PABX. 1 The local serving switch point connectivity with the PSTN. With the exception of the subscriber plant, the PSTN has evolved to an a