A noise gate is a type of guitar effects pedal used to reduce unwanted noise and hum in the guitar signal chain. It works by automatically muting or attenuating the signal when it falls below a certain threshold, effectively “gating” out background noise during silent passages or when the guitar is not being played.

Here are the key features and functions of a noise gate pedal:

1. **Threshold**: The threshold control sets the level at which the noise gate activates. Any signal below this threshold will be attenuated or muted. Adjusting the threshold allows users to customize the sensitivity of the noise gate to match the level of background noise in their signal chain.

2. **Decay (or Release)**: The decay control determines how quickly the noise gate closes after the signal falls below the threshold. A shorter decay time results in a faster response, while a longer decay time allows for a more gradual fade-out. This control helps to smooth out the transition between active and muted signal states.

3. **Attack (or Hold)**: Some noise gate pedals feature an attack control, which determines how quickly the gate opens when the signal exceeds the threshold. This control can be useful for preserving the initial transient of guitar notes and preventing them from being cut off abruptly.

4. **Range (or Depth)**: The range control adjusts the amount of attenuation applied to the signal when the noise gate is active. Increasing the range increases the amount of signal suppression, effectively reducing background noise and hum.

5. **Release (or Hold)**: The release control sets the amount of time the gate remains closed after the signal falls below the threshold before reopening. This control helps to avoid chopping off sustained notes or chords prematurely by allowing the gate to stay closed for a specified duration.

Noise gate pedals are commonly used in guitar rigs to eliminate unwanted noise from high-gain amplifiers, noisy effects pedals, or noisy venues. They can help improve the overall clarity and definition of the guitar tone by reducing background noise and hum, especially during quiet passages or when using high levels of distortion or gain.

Overall, noise gate pedals are valuable tools for guitarists looking to achieve cleaner, more articulate tones by effectively controlling unwanted noise in their signal chain.