Extended system functionality

In a basic 2-wire apartment system, just the DX door station itself can give the system more functions, such as memory, divert function, and IP camera access. No need additional accessory, like IPG at all.

The advantages of the new solution over the original IPG solution are：

The memory is changed to video record, and also improve the recording image quality (720P)
With the new technical solution, the call transfer is faster, and the APP image has been greatly improved from 320*240 to 640*480
Supports a wider range of IP camera types, mobile viewing, also PiP and Quad function

Management and application of IP camera in DX system-待修