The Judder is a hold / freeze effect which uses a momentary footswitch which, when depressed, engages the effect. 

There are 3 modes of operation:

Stutter

A mute effect which stops any sound coming out of the pedal. Commonly called a ‘Killswitch’.

Judder

The ‘classic’ Judder effect. When the button is pushed the previous split second of sound is repeated endlessly. The length of this period of time is set by the Rate and Dirt controls.

Layers

This option allows the user to keep adding guitar to the repeated section for a “Sound on Sound” effect.

Other switching features include:

True Bypass

In order to achieve the effect, this pedal requires that the input signal is routed through the on board preamp at all times. Although the preamp is of great quality and transparency some purists may require their signal to fully bypass the pedal, this can be done by using the Bypass toggle switch. 

Dirt Mode

By pushing the delay chip to its limits it is possible to achieve several seconds of repeated sound. This longer time limit comes at a cost, such as noisier operation and lower bit rate which is why it is named Dirt. In some situations this might be desirable and can be a lot of fun.