1-36. 1-37. 1-38. 1-39. 1-40. 1-41. 1-42. BFSK AFTS Interrupting  the  cycle  at  a degree point and changing the direction  or  amplitude  of the  sine  wave Which  of  the  following  modes  of modulation can be used to modify carrier signals to convey data? 1.  Phase  modulation 2.   Frequency   modulation 3.   Amplitude   modulation 4.  All  of  the  above In  which  of  the  following  modulation methods  are  frequencies  above  and  below a center frequency used to indicate a logic 1 or 0 bit? 1.   Amplitude   modulation 2.   Frequency-shift   keying 3.   Audio   frequency   tone   shift 4.  Differential  quadratic  phase-shift keying Which  of  the  following  modulation methods uses two discrete audio tones that are modulated to a constant frequency carrier  signal? 1 .    F S K 2.   BFSK 3.  AFTS 4.   Phase-shift   keying When  quadrature  phase-shift  modulation is used, a single tone transmits what total number of binary bits of data for each phase Shift? 1 .    O n e 2.     Two 3.   Three 4 .    F o u r 1-43. When  quadrature  phase-shift  modulation is used, which of the following phase shifts indicates a binary 00? 1 . +135  degrees 2. –135  degrees 3 . +225  degrees 4. –225  degrees 1-44. Which of the following components of a modem converts the data bits into a carrier  signal? 1.  The  transmitter 2.  The  receiver 3.  Both  1  and  2  above 1-45. Each  modem  transmitter  circuit  outputs several carrier signals. 1.   True 2.   False 1-46. Which of the following circuits allows ONLY  the  desired  carrier  signal  to  be received  from  the  communications channel? 1.  The  demodulator 2.  The  data  decoder 3.  The  band  pass  falter 4.   The   receiver   control   circuit 1-47. The  term  baud  describes  the  number  of characters  per  second  transmitted  over  a communications channel. 1.   True 2.   False 5