Yealink SIP-T48G - What will happen if I connect both PoE cable and power adapter? Which has the higher priority?; Why does the IP phone use DOB format logo file instead of popular BMP, JPG and so on?

Administrator’s Guide for SIP-T2 Series/T19(P) E2/T4 Series/CP860 IP Phones
790
IP phones use the PoE preferentially.
The IP phone only uses logo file in DOB format, as the DOB format file has a high
compression ratio (the size of the uncompressed file compared to that of the
compressed file) and can be stored in smaller space. Tools for converting BMP format to
DOB format are available. For more information, refer to Customizing a Logo Template
File on page 179.