In the Telephone Receiver?

a device, as in a telephone, that converts changes in an electric current into sound.

What does it mean by telephone receiver?

: a device (as in a telephone) for converting electric impulses or varying current into sound.

Which part of the phone is the receiver?

Receiver. The receiver is located in the earpiece of the telephone's handset. Operating on electromagnetic principles that were known in Bell's day, it converts fluctuating electric current into sound waves that reproduce human speech.