Communication apparatus

A method for preventing a communication error at a called station capable of communicating according to protocols of Recommendations T.30, V.8, and V.34 of the ITU-T, comprising:

• sending a first ANSam signal from the called station to a calling station, said first ANSam signal being sent for a predetermined transmission period;
• waiting to receive a first CM signal from the calling station within the predetermined transmission period;
• transmitting a DIS signal having bit number 6 set to the calling station if the first CM signal is not received within the predetermined transmission period;
• receiving one of a DCS signal and an NSS signal from the calling station;
• receiving a CM signal from the calling station;
• sending a JM signal to the calling station;
• executing communication with the calling station in accordance with the V.34 protocol after reception of a CJ signal from the calling station,
• wherein the preceding steps are accomplished after transmitting a DIS signal having bit number 6 set and before receiving either the DCS signal or the NSS signal from the calling station;
• and
• executing communication with the calling station in accordance with the T.30 protocol after reception of either of the DCS or NSS signals from the calling station.

A method for preventing a communication error at a calling station capable of communicating according to protocols of Recommendations T.30, V.8, and V.34 of the ITU-T, comprising:

• sending a first CM signal to the called station after receiving a first ANSam signal from the called station;
• executing communication with the called station in accordance with the V.8 protocol if a JM signal is received from the called station;
• sending a CI signal from the calling station to the called station if the first ANSam signal is not received from the called station and if a DIS signal having bit number 6 set is received from the called station;
• receiving a second ANSam signal from the called station;
• sending a second CM signal to the called station;
• executing communication with the called station in accordance with the T.30 protocol if the first ANSam signal is not received from the called station and if a DIS signal without bit number 6 set is received from the called station;
• and
• executing communication with the called station in accordance with the V.8 protocol if the JM signal is received from the called station.

A method for preventing a communication error at a calling station capable of communicating according to protocols of Recommendations T.30, V.8, and V.34 of the ITU-T, comprising:

• sending a first CM signal to the called station after receiving a first ANSam signal from the called station;
• executing communication with the called station in accordance with the V.8 protocol if a JM signal is received from the called station;
• executing communication with the called station in accordance with the T.30 protocol if the first ANSam signal is not received from the called station and if a DIS signal without bit number 6 set is received from the called station;
• stopping transmission of the first CM signal to the called station after receiving a V.21 channel 2 signal from the called station;
• receiving a DIS signal;
• executing communication with the called station in accordance with the T.30 protocol if the DIS signal does not have bit number 6 set;
• and
• executing communication with the called station in accordance with the V.8 protocol if the DIS signal has bit 6 set.