24 Figure 3F. Solid-state schematic symbols. IN ANSWERING QUESTIONS 3-45 THROUGH 3-47, SELECT FROM FIGURE 3-F THE SCHEMATIC SYMBOL IDENTIFIED IN THE QUESTION.   3-45.   Schematic symbol for a photo-diode.   1.    A   2.    B   3.    C   4.    D 3-46.   Schematic symbol for a two-terminal phototransistor.   1.    A   2.    B   3.    C   4.    D 3-47.   Schematic symbol for a three-terminal phototransistor.   1.    A   2.    B   3.    C   4.    D 3-48.   Which of the following devices is similar in operation to a photodiode?   1.    Phototransistor   2.    Photocell   3.    LED   4.    SCR 3-49.   Which of the following is a typical light to dark resistance ratio of a photocell?   1.    1:      10   2.    1:     100   3.    1:   1000   4. 1:10,000 3-50.   Photocells are used in which of the following circuits?   1.    Controller   2.    Oscillator   3.    Amplifier   4.    Detector 3-51.   How should photovoltaic cells be coupled together to produce a relatively high voltage?   1.    Series coupling   2.    Parallel coupling   3.    Inductive coupling   4.    Mechanical coupling 3-52.   What is the total number of terminals in a unijunction transistor (UJT)?   1.    One   2.    Two   3.    Three   4.    Four 3-53.   The UJT has which of the following advantages over the conventional transistor?   1.    Fewer terminals   2.    Larger bandpass   3.    Less bias is required   4.    Increased temperature stability