1．stop transmission and wait, +fts=[time]

    the command +fts=[time] causes the dce to stop any transmission. the dce then waits for the specified mount of time, and then sends the ok result code to the dte. the value [time] is in 10 millisecond intervals.

    2．receive silence, +frs=[time]

    the command +frs=[time] causes the dce to listen, and to report back an ok result code when silence has been present on the line for the amount of time specified. the value [time] is in 10 millisecond intervals. the command will terminate when the required amount of silence on the line is detected or the dte sends the dce another character, which is discarded. in either event, the ok result code ,will be returned to the dte.

    3．facsimile transmit, +ftm=[mod]

    the command +ftm=[mod] causes the dce to transmit data using the modulation selected in [mod]. [mod] may have the values shown in section 1.1.

    the dce returns the connect result code and transmits the proper training sequence in the selected mode, followed by constant 1 bits, until data is received from the dte.

    the dce buffers data in this mode. the configured flow control method will be used by the dce as necessary to pause the dte.

    if the dces transmit buffer becomes empty and the last transmitted character is ascii nul (00), the dce shall continue to transmit nuls until the dte sends more data or 5 seconds elapses. after 5 second elapse with an empty transmit buffer, the dce will turn off transmit carrier and return to command state, returning the error result code.

    note: 00 replication is useful for generating tcf (1.5 seconds of os) and zero-fill within lines.

    when the dces transmit buffer becomes empty and the last transmitted character was not nul, the dce shall turn off transmit carder, return to command state and send the ok result code to the dte.

    4．facsimile receive, +frm=[mod]

    the command +frm=[mod] causes the dce to enter receive mode using the modulation specified in [mod]. [mod] may have the values shown in section 1.1

    when the selected carrier is detected, the dce will send the connect result code to the dte.

    the dce shall return to command state upon loss of carrier, and send the no carrier result code to the dte.

    the dce shall obey the configured flow control from the dte. if the dte sends any character to the dce other than dc1 or dc3 while the dce is in this mode, the dce shall enter command state and send the ok result code to the dte.

    5．hdlc transmit, +fth=[mod]

    the command +fth=[mod] causes the dce to transmit data framed in hdlc protocol using the modulation mode selected. [mod] may have the values shown in section 1.1.

    the dce will send the connect result code to the dte, and transmit signal converter training (if required) followed by flags until the first byte of data is sent by the dte.

    when the buffer becomes empty the dce shall compute and append the frame check sequence (fcs) and a closing flag to the frame. the dce will insure that the minimum number of flags required by t.30 are sent before the data from the dte begins to be transmitted.

    the dce shall check the final frame bit in the control field of each frame; this is the 5th received bit of the second byte of each frame. if the final frame bit is 1, the dce shall cease transmitting after the frame is sent, return to command state, and send the ok result code to the dte. if the final frame bit is 0, the dce shall send the connect result code to the dte and continue to transmit flags unfit one of the following actions is taken by the dte:

    1 if the dte sends additional data, the dce shall transmit another frame.

    2 if the dte sends only [dle] [etx] (a null frame), the dce shall turn off transmit carrier and send the ok result code to the dte.

    3 if 5 seconds elapses from the time when the dce reported the connect result code without any additional data transmitted from the dte, the dce shall turn off transmit carrier, return to command mode, and send the error result code to the dte.

    the dce performs hdlc transparency functions and fcs generation while in this mode.

    the dce buffers data in hdlc transmit mode. the dce will use the configured method of flow-control to pause the dte as necessary.

    6．hdlc receive, +frh=[mod]

    the command +frh=[mod] causes the dce to receive hdlc framed data using the modulation mode selected in [mod], and deliver the next received frame to the dte. [mod] may have the values shown in section 1.1.

    if the dce detects the selected carrier with an hdlc flag, the dce shall send the connect result code to the dte. the dce will return to command state upon loss of carrier, sending the no carrier result code to the dte.

    the dce strips flags, and receives and buffers frames. the received data, starting with the first non-flag byte and continuing through the last fcs byte shall be transferred to the dte. the dte should ignore the value of the fcs bytes. the dce performs hdlc zero-bit deletion and error checking.

    after the fcs bytes are transferred, the dce shall mark the end of the frame with the characters [dle][etx], and report the status of the frame reception to the dte:

    if the frame was received correctly (fcs is ok), the dce shall return the ok result code.

    if the frame was received in error (fcs is not ok, or carrier lost, or data lost due to data overflow), the dce shall return the error result code; the dte should discard the frame.

    after the status result code, the dce shall accept new commands from the dte.

    the dce shall obey the configured flow control from the dte. if the dte sends any character to the dce other than dc1 or dc3 while the dce is in this mode, the dce shall enter command state and return the ok result code.

    after sending the result code indicating that frame reception is complete, the dce shall continue to receive and buffer data in the selected mode. if the dte issues another +frh=[mod] command, the dce shall return another connect result code and continue with hdlc reception. if the dte issues any command that changes modulation, the dce shall stop the receive process; any buffered data will be discarded and the command will be obeyed.