A facsimile transmission control procedure for a relay use to relay facsimile communication via a public telephone network between mobile communication control units placed at different places from one another in which such facsimile communication is implemented by the use of a radio link wherein non-standard facilities signal NSF and non-standard facilities set-up signal NSS defined by the Recommendation T.30 are used to identify another communicating party; if the other communicating party can apply a transmission control procedure of the invention, communication is conducted in accordance with such independent transmission control procedure, while if it is not, the communication is made based on the standard Recommendation T.30; and in the independent transmission control procedure, a time margin of each preamble, which is to be added to each of all the binary code signals used in the communication on and after an exchange of NSF and NSS between transmission and reception sides was executed, is reduced to a predetermined time.