- The encoders in the telephone converts sound energy into electrical energy
- When a person speaks into a telephone, the sound energy is taken in by the encoder
- Therefore, when a person speaks into a telephone, the sound energy is converted into electrical energy by the encoder

So, when a person speaks into a telephone, the sound energy is converted into electrical energy by the encoder
When a person speaks into a telephone, sound energy is changed mostly into which form of energy?
- The encoders in the telephone converts sound energy into electrical energy 
- When a person speaks into a telephone, the sound energy is taken in by the encoder