The IndiPRO Tools Mini-Tap with Panasonic DMW-BLF19 Dummy Battery Cable allows you to simultaneously power the Panasonic GH5/GH4 camera and up to two other devices from a V-Mount or Gold Mount battery that has a D-Tap port. It's also inline-regulated to prevent causing noise/heat in the camera. (The GH5 and GH4 cameras require a regulated voltage source.)
On one end, the cable features a T-shaped component with a male D-Tap connector on the bottom, a female D-Tap port on the side, and a USB port on the other side. The male D-Tap is for plugging into the V-Mount/Gold Mount battery, sold separately. On the other end of the cable is a DMW-BLF19 dummy battery compatible with the GH5 and GH4 cameras.
The USB port outputs 5V of power at up to 2A, allowing you to connect most mobile and select audio devices on set.