Specs:

9-18VDC operation, green circuit design pulling only 30mA of current. Tiny package! only 3.9″ wide x 4″ deep x 2.5″ tall. 16 gauge cold rolled steel chassis with easy battery access via 2 thumbscrews. Like the ST-1, controlled by the Fulltone-designed and manufactured Opto-1 Photocell.
True-Bypass switching with Bright Red LED & exclusive Fulltone “No-Pop” circuit. Constantly flashing Blue LED for Tempo (even when pedal off to easily match song)
100% Built in the USA. Tap-Tempo. External Tap jack! Half/Double feature accessed by holding down Tap switch for ¾ of a second. Up to 15dB boost (cool feature!) Turn “Mix” knob all the way down and the pedal becomes the world’s best clean boost pedal! Top-mounted jacks and DC port. 3 switchable waveforms: Square, (modified)Sine, and (heartbeat-like) Warble wave-forms. Digital Brain (for the oscillator only) with 100% analog signal path. Unlike the ST-1, the Jr can do speeds so slow that a full cycle takes around 10 seconds, and fast speeds beyond 220bpm. The heart of the ST-1 is still there, the warm Analog Devices JFET preamp. And this pedal is so small it will fit in your pocket, and with its top-mounted jacks, will fit in any little spot on your board. Just like the ST-1, the Jr also works as an incredible clean boost with the Mix control turned down!