With the help of the D-Tab cable, for example, dummy batteries can be connected to an external power source. Newell V-lock batteries usually have such a connector. A dummy battery that can be placed in a specific camera can be connected to such a V-lock battery to increase the continuous operating time of the camera many times. This is important if we want to work with the camera in such a way that it is not possible to interrupt the work by changing the battery. For example, in astrophotography, when you have to continuously expose for several hours with specific shutter speeds and intervals.