Communication apparatus for generating a call signal from a telephone set to a data terminal
AssigneeCanon Kabushiki Kaisha
InventorShoji Suzuki
Life of this patent
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Abstract
A call signal generating circuit includes a DC/DC converter, an ON/OFF control unit, including a control circuit and a phototransistor, for ON/OFF-controlling an output voltage from the DC/DC converter, and a polarity inverter cooperating with the control circuit, for switching polarities of an ON/OFF-controlled voltage. The ON/OFF timings of the ON/OFF control unit and a polarity switching timing of the polarity inverter are adjusted to generate a call signal having an arbitrary frequency.
Claims22
A call signal generating circuit comprising:
- a DC/DC converter;
- ON/OFF control means for ON/OFF-controlling an output voltage from said DC/DC converter;
- and
- polarity switching means for switching polarities of an ON/OFF-controlled voltage.
A communication apparatus comprising:
- means for connecting a line to a data communication unit;
- means for generating a call signal for starting the data communication unit;
- means for detecting a response of the data communication unit in response to the call signal;
- and
- control means for interrupting generation of the call signal and causing said connecting means to connect the line to the data communication unit on the basis of an output signal from said detecting means,
- wherein said call signal generating means comprises
- a DC/DC converter;
- ON/OFF control means for ON/OFF-controlling an output voltage from said DC/DC converter;
- and
- polarity switching means for switching polarities of an ON/OFF-controlled voltage.
A communication apparatus comprising:
- means for connecting a line to a data communication unit;
- means for generating a call signal for starting the data communication unit,
- wherein said call signal generating means generates the call signal while a ground level is being insulated,
- means for detecting a response of the data communication unit in response to the call signal;
- and
- control means for interrupting generation of the call signal and causing said connecting means to connect the line to the data communication unit on the basis of a detection signal from said detecting means.
A communication apparatus comprising:
- means for connecting a line to a data communication unit;
- key input means for inputting dial data of a destination;
- means for sending a dial signal corresponding to a key input by said key input means;
- means for storing an accessory telephone set connecting line of the data communication unit and forming a DC loop of the accessory telephone set connecting line;
- means for sending the call signal to the data communication unit;
- means for detecting a response of the data communication unit received in response to the call signal from said call signal sending means;
- and
- control means for causing said connecting means to connect the line to the data communication unit on the basis of a detection signal from said response detecting means.
Dependencies are inferred from the claim text.