21 3-7.   Assume that two signals are received, one at 500 kHz and the other at 501 kHz. What frequency, in kHz, should be mixed with them to distinguish the 501 kHz signal by producing a 1 kHz output? 1. 499 2. 500 3. 501 4. 502 Figure 3B.—Detector. IN ANSWERING QUESTIONS 3-8 THROUGH 3-11, REFER TO FIGURE 3B. 3-8.   The detector circuit in the figure uses the heterodyning principle to detect the incoming signal. What type of detector is it? 1.  Hartley 2.  Colpitts 3.  Armstrong 4.  Regenerative 3-9.   What component controls the operating frequency of the detector? 1. C1 2. C2 3. L2 4. R1 3-10.   What component provides the feedback necessary for oscillations to occur? 1. R1 2. C2 3. C3 4. L2 3-11.   Which of the following circuit functions does Q1 perform? 1.  Mixer 2.  Detector 3.  Oscillator 4.  Each of the above 3-12.   A circuit that is nonlinear, provides filtering, and is sensitive to the type of modulation applied to it fulfills the requirements of which, if any, of the following circuits? 1.  Mixer 2.  Modulator 3.  Demodulator 4.  None of the above 3-13.   A detector uses which of the following signals to approximate the original waveform? 1.  The sum frequency 2.  The carrier frequency 3.  The modulation envelope THIS SPACE LEFT BLANK INTENTIONALLY.