A device labelled "Gain = 10 dB" is likely to be an:

A positive gain value expressed in decibels (dB) indicates that a device increases the strength of a signal passing through it. Devices designed specifically to increase signal strength are amplifiers. For example, a gain of 10 dB means the output power is ten times greater than the input power. An attenuator or an audio fader would have a negative gain (or positive attenuation) because they are designed to reduce signal strength. An oscillator generates its own signal rather than amplifying an external input by a set gain factor.