B-004-001-001

A circuit designed to increase the level of its input signal is called:
A) an oscillator

B) an amplifier

C) a modulator

D) a receiver

The answer is B.
An amplifier increases the power of a signal. It amplifies it. So, the circuit designed to increase the level of the its input signal is an amplifier.

What is an amplifier?

What is an Oscillator?

[https://en.wikipedia.org/wiki/Modulation What is a Modulator? (Modulation)]

What is a Receiver?

Beginners guide to ham radio