If you receive 1s and 0s or if you receiver currents and voltages you would not be able to understand what is being transmitted, so these voltages and current have to be converted in the form that you can understand and the form that you can understand is perhaps the language that we are speaking right now.
अगर आप १ और ०प्राप्त करते हैं या आप करंट और वोल्टेज प्राप्त करते हैं तो समझ नहीं पाएंगेकि क्या संदेश पहुंचाया गया है।