Keep your camera continuously powered without any interruptions by using the Tether Tools Case Relay Camera Power System. It features an inbuilt 7.4 V, 1200 mAh lithium battery, and a 5 VDC input via USB, which help in providing power when connected to an external power source. When connected to an AC adapter or a 2 A USB battery pack, the Case Relay can still provide a constant supply of power to your camera. Use the internal battery to enable the system to support hot swapping of external power sources. Also, the LED indicator light shifts from green to yellow to red in order to show the amount of battery power remaining in the Case Relay.