13 2-17.   What is the schematic symbol for a crystal? 1. 2. 3. 4. 2-18.   What electrical characteristic makes the frequency stability of a crystal better than that of an LC tank circuit? 1.  Higher Q 2.  Higher inductance 3.  Higher resistance 4.  Higher capacitance 2-19.   How is feedback described? 1.  Control of a circuit output signal by the input signal 2.  Control of a circuit input signal by the output of the previous circuit 3.  Transfer of a portion of the output circuit energy to control the input of the circuit 4.  Transfer of a portion of the input circuit energy to control the output circuit 2-20.   Which of the following terms describes the types of feedback? 1.  Degenerative and regenerative 2.  Negative and positive 3.  Both 1 and 2 above 4.  Bypassed and unbypassed 2-21.   What type of feedback aids an input signal? 1.  Positive 2.  Negative 3.  Bypassed 4.  Degenerative 2-22.   What type of feedback opposes an input signal? 1.  Positive 2.  Unbypassed 3.  Degenerative 4.  Regenerative 2-23.   What type of feedback is used to sustain oscillations? 1.  Bypassed 2.  Negative 3.  Degenerative 4.  Regenerative 2-24.   What oscillator uses a tickler coil for feedback? 1.  Hartley 2.  Colpitts 3.  Armstrong 4.  RC phase-shift 2-25.   What oscillator uses a tapped coil for feedback? 1.  Hartley 2.  Colpitts 3.  Armstrong 4.  RC phase-shift