For older models, the AC adapter provides power while also extended a USB input for plugging in via the back port.

ENGADGET: Kinect for Xbox 360 review

The High Power AC Wi-Fi Adapter adds long range 802.11ac Wi-Fi connectivity to Windows or Mac Ultrabooks, laptops and desktops.

ENGADGET: Amped Wireless announces a new range of 802.11ac high-powered WiFi routers

Toward the right, you've got the USB type B connector that runs to your laptop, the AC adapter jack, and the master power switch.

ENGADGET: Native Instruments Traktor Kontrol S4 review Alt

The only digs were its lack of an included AC adapter (you're forced to use USB power) and subsequently, its honest inability to be used as a mobile solution.

ENGADGET: Creative Xmod external X-Fi device reviewed

Yes, that's right, we said AC adapter jack: unlike the X1, the S4 can't be driven off bus power alone, unfortunately.

ENGADGET: Native Instruments Traktor Kontrol S4 review Alt