The D-SX9 is for Sony’s FX9 camera using the v mount batteries to power the camera rather than the standard BPU batteries. It’s attached to the top of the camera with the included screws.
It has a 19.5V output with a low warning LED, LED will flash when the battery is low, giving you a chance to exchange the battery.

Specifications:
Input: DC 12-17V
DC Output: DC19.5V  4A
D-tap Output: DC12-17V
Weight:0.45kg
Dimension: 149x110x75mm