Not all stompboxes and rackmounted electronic devices designed for musicians are effects. Strobe tuner and regular electronic tuner pedals indicate whether a guitar string is too sharp or flat.[110] Stompbox-format tuner pedals route the electric signal for the instrument through the unit via a 1/4" patch cable. These pedal-style tuners usually have an output so that the signal can be plugged into a guitar amp to produce sound.