Inspired by our Expression System technology, the Expression System Transducer, or ES-T™, is a single-source, under-saddle transducer with individual elements for each string. (The ES-T was originally called the ES Element, but the name was changed to avoid confusion with another product.) The ES-T has an onboard preamp and the same active controls found on the full Expression System. Featuring a custom-voiced EQ and dynamic response, the system is powered by a 9-volt battery, with a battery life LED power indicator (which is lit when the battery is being used). The pickup also has a Phase switch for feedback control, which is located on the preamp board inside the soundhole.