# Viewpoint of DIS(DTS)/DCS

Before starting communication, faxes communicate their own functions on the sending side and the receiving side, and then determine the communication function and speed.
The receiving side fax machine transmits its own function to the sending side fax machine by the DIS signal.
The sending fax machine receives the DIS signal from the receiving fax machine and can use the information on the sending side and the receiving side.
After selecting the maximum function set by the transmission side, you can check the communication mode selected by the DCS signal
By checking the information of DIS (DTC), the contents of the capability of the receiving side fax can check the communication mode selected by the sending side fax by checking the information of the DCS.
The protocol monitor log is recorded and printed on only one sheet by one communication.
If the protocol becomes long due to communication of a plurality of pages and it does not fit on one page, the head protocol log is deleted and only the last protocol log is recorded and printed.
Fax communications are created according to ITU, and the main ITUs involved are T30. and T4.
DIS (DTC) DCS reads out the content of FIF (facsimile information field) by referring to the bit allocation table of DIS (DTC) / DCS.