Define modulation and transducer.

Explanation

Modulation: For efficient transmission and reception of signals, it is superimposed on a high frequency wave, some characterstic of which varies as a function of the instanteous value of the signal and so resulting wave produced is transmitted.
The signal is called 'modulating wave' , the high frequency wave is called 'carrier wave' and the resulting wave is called 'modulated wave'. This process is called modulation.
Transducer: A transducer is a device which converts one form of the energy into another form. The message from the information sources may or may not be electrical in nature. When the message signal produced by information source is not electrical in nature, an input transducer is used to convert it into a time varying signal. For example, in radio-broadcasting, a microphone converts the information (sound waves) into corresponding electrical signal.