SMS Type 3 Fax

Does not affect your reply to text messages. If the other party has set up Category 3 fax, small 8 will reply to Category 3 fax mode by default when you reply. Of course, you can also see it when replying to each other in SMS mode. In fact, it is meaningless for a mobile phone to send text messages to a mobile phone, and it is also meaningless to set up three types and four types of faxes. These are actually for fax machines.

For example, all three fax standards are coding programs with one-dimensional stroke length, where "one-dimensional" means that each continuous horizontal line is coded independently of other lines, and "stroke" means that each line can be divided into alternating pixel segments of the same color-white stroke, black stroke, white stroke, black stroke, etc. In this way, three types of faxes will reproduce your content on paper according to the strokes. However, the four types of faxes use the two-dimensional code program. If the documents to be sent have spatial redundancy in the vertical direction (as most documents do), Class 4 fax machines can make full use of these redundancies, so the compression efficiency of most fax documents in Class 4 is higher than that in Class 3. Category 4 is a superset of Category 3, because Category 4 devices need to receive Category 3 files.

Personally, I think that the reason why SMS supports so many types at present is to be compatible with more information modes at most, and more is just a gimmick.