This is what Digitech say about the Drop:
The DigiTech Drop is a polyphonic drop tune pedal that allows you to drop the tuning of your guitar from one semitone all the way down to a full octave. You can get anything you want - from a fully down-tuned chunk to just a little extra depth without having to swap ypur guitars. A great feature of the Drop pedal is it has a momentary/latching switch. With the switch set to the momentary mode, you can turn the drop into a true 'on the fly' performance pedal. Rage Against the Machine eat your heart out....!
• 9 Drop Effect Settings
• Momentary On/Off Switch
• True Bypass
• Compact Design
• Solid Construction
• Included Power Adapter