a: Power supply unit
b: Transmitter c: Tuner
d: Heat sink
4. How can we measure the frequency of a periodic sign by an oscilloscope?
a: We identify the number of the vertical dividing when the picture on the screen is fixed
b: We identify the number of the horizontal dividing when the picture on the screen is fixed
c: We identify the number of horizontal dividing that belongs to one complete period, multiply it by the timebase value of the switch state then take the reciprocal of the result
d: We can not measure frequency with an oscilloscope