Data communication apparatus and method capable of discriminating calling stations

A data communication apparatus, comprising:

• means for detecting a calling signal on a communication line;
• means for transmitting a data communication procedure signal onto the communication line in response to detection of the calling signal;
• and
• means for discriminating whether the signal on the communication line is a procedure signal for data communication or a voice signal for voice communication, by using a tonal counter which counts a number of times that each of a plurality of frequencies is respectively detected in the calling signal for recognizing a tonal signal of the procedure signal, wherein said transmitting means repeatedly transmits a data communication procedure signal until said discriminating means discriminates whether the calling station is a data communication apparatus or a voice terminal, during discrimination by said discriminating means, and wherein said discriminating means discriminates whether or not the calling station is a data communication terminal or a voice terminal in accordance with whether a selected one of the numbers obtained by the tonal counter exceeds a predetermined value.

A data communication apparatus, comprising:

• means for sampling frequency data on a communication line in response to reception of a calling signal from a calling station;
• and
• means for discriminating whether the calling station is a data communication terminal or a voice terminal, in accordance with a distribution of frequency data obtained by said sampling means,
• wherein said discriminating means discriminates whether or not the calling station is a data communication terminal or a voice terminal, in accordance with a ratio of a number of the frequency data having a particular characteristic to a total number of frequency data obtained by said sampling means.

A data communication method for use in a called station having a tonal counter which counts a number of times that each of a plurality of frequencies is respectively detected in a received signal and recognizes a tonal signal of procedure signals for data communication, said method comprising the steps of:

• detecting a calling signal from a calling station;
• discriminating a kind of signal present on a communication line, in response to the calling signal;
• determining whether the calling station is a data communication terminal or a voice terminal in accordance with the kind of signal discriminated in said discriminating step by using the tonal counter;
• and
• repeatedly sending a procedure signal for data communication until the type of the calling station is determined by said determining step, during said determining step,
• wherein, in said determining step, it is determined whether the calling station is a data communication terminal or a voice terminal in accordance with whether a selected one of the numbers obtained by the tonal counter exceeds a predetermined value.