Answer :
Pulse type of modulation is applied to radio-controlled toys, therefore the correct answer is option D.
What is the frequency?
It can be defined as the number of cycles completed per second. It is represented in hertz and inversely proportional to the wavelength.
Toys controlled by remote control operate by emitting infrared radiation. These infrared rays have a frequency of 34–48 kilo Hertz.
Different types of modulations, such as frequency and amplitude modulation for transmitting and receiving video and music, are employed for other reasons.
Thus, the Pulse-type of modulation is applied to radio-controlled toys, therefore the correct answer is option D.
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