JP2004187120A - Communication equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide communication equipment capable of detecting that another telephone is off-hooked without separately providing an off-hook detection circuit for the telephones provided together. <P>SOLUTION: This communication equipment 301 using a silicon DAA that is connected to the telephone lines to perform data communication has a DAA circuit 317 for measuring the voltage of the telephone lines before off-hook when a host 302 for controlling the communication equipment 301 outputs an instruction for a communication start in the telephone lines where a second telephone set 314 is provided together on the telephone lines, and a DSP 303 for recognizing that the external telephone set 314 connected parallelly to the same telephone lines are off-hooked, stopping starting communication and notifying the host of the stopping of the communication start when the measured value is not higher than a preset threshold. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a built-in data communication device connected to a public line such as a BS / CS digital set-top box, a BS / CS digital TV, a facsimile / telephone device with a communication function, and the like.
[0002]
[Prior art]
2. Description of the Related Art A conventional technology of a modem is described as an example of a data communication device connected to a public line. At present, interactive services are provided in new broadcasting services such as BS digital broadcasting. For such a two-way service, a BS digital TV or a BS / CS digital set-top box has a built-in modem device for performing data communication. These devices include a host controller (microcomputer, CPU, etc.) that controls the inside, and controls a modem device connected to a telephone line.
[0003]
The BS / CS digital set-top box and the like use this modem to perform data communication, transmit billing information, and download information from the Internet. In such a device, a telephone is always occupied in parallel on the same telephone line, not occupying the telephone line.
[0004]
In such a case, if a device having a modem attempts to start communication, if the attached telephone is in an off-hook state (a state in which the handset is lifted), it is possible to dial normally even if dialing is performed as it is. It is not possible to ring, and it is necessary to stop the communication to prevent the user's communication from being interrupted. In order to check the use state of the attached telephone, it is necessary to separately provide an off-hook detection circuit for the attached telephone to determine whether or not current is flowing through the telephone line.
[0005]
[Patent Document 1]
JP 2000-513186 A
[Problems to be solved by the invention]
FIG. 3 shows an example of an off-hook detection circuit of an attached telephone. When the attached telephone is off-hook, the transformer of the attached telephone is closed, and the line is connected. Since the current flows through the line and also flows through the photocoupler 205, the current detection signal becomes low, and it can be checked whether the attached telephone is in an off-hook state. However, the provision of a separate circuit increases the cost, and in many cases, there is no function of detecting that the attached telephone is off-hook at the start of communication. In FIG. 3, 201 is a modem, 202 is a telephone line, 203 is a 100Ω resistor, 204 is a varistor, and 205 is a photocoupler. As a reference describing a conventional technique of a DAA (Data Access Arrangement) circuit having an off-hook / on-hook detection circuit of a co-located telephone, there is, for example, Patent Document 1 described above.
[0007]
An object of the present invention has been made in view of the above circumstances, and in a communication device connected to a telephone line, an off-hook of an attached telephone can be easily detected without providing a separate off-hook detection circuit of the attached telephone. To provide a communication device.
[0008]
[Means for Solving the Problems]
The communication device according to the present invention is a device that performs data communication by connecting to a telephone line, and in regard to a telephone line in which another telephone is connected to the telephone line, an instruction to start communication is issued from a host that controls the communication device. When a call is issued, a DAA circuit that measures the voltage of the telephone line before going off-hook and an external telephone connected in parallel to the same telephone line goes off-hook if the measured value is equal to or less than a preset threshold value. And a DSP for recognizing that the communication is stopped, stopping communication start, and notifying the host of the stop.
[0009]
In the communication device according to the present invention, the preset threshold value can be set as a parameter from outside.
[0010]
Recently, silicon DAAs have been used instead of conventional transformers using windings, which replace their functions in integrated circuits. Among the functions of this silicon DAA, there is a function that can measure the line voltage. The line voltage is lower when the attached telephone is off-hook than when the line is open because the line is closed. Therefore, the off-hook state of the attached telephone can be detected by checking the voltage of the telephone line before going off-hook. That is, the line voltage is checked before the modem goes off-hook, and if the voltage is lower than a certain value, it can be determined that the attached telephone is off-hook.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
A specific embodiment will be described using a modem as an example of a communication device connected to a public line.
[0012]
FIG. 1 shows a configuration of a modem device using a recent silicon DAA. Reference numeral 301 denotes a modem chip, in which a DSP (digital signal processor) core 303 (a CPU core may be provided), a ROM 307, a RAM 308, a silicon DAA interface 306, a communication I / O 304, and an NCU (network control unit) control A built-in I / O 305 is provided. The modem 301 is connected to a host 302 such as a personal computer or a microcomputer by a communication I / O 304 (serial communication I / O or parallel communication I / O), and is controlled by a command generally called an AT command. The AT command has a form in which the first character of the command starts with "AT" or "at", and is followed by the command.
[0013]
Reference numeral 311 denotes a system side device chip of the silicon DAA 317, and 313 denotes a line side device chip of the silicon DAA 317. Reference numeral 312 denotes a capacitor for an isolation barrier for electrically isolating the primary side and the secondary side. Through this capacitor 312, the system side device 311 and the line side device 313 of the silicon DAA 317 communicate with each other. The modem 301 and the silicon DAA 317 exchange status and commands via serial communication and control the modem 301.
[0014]
The system-side device 311 performs data communication with the line-side device 313 to give an off-hook signal 309 as an off-hook instruction to the line-side device 313, line current value data at the time of off-hook from the line-side device 313, a ring signal 310, etc. Or receive. Further, during communication, it receives transmission data for performing D / A conversion to the line and A / D conversion data from the line, and transmits and receives data to and from the DSP 303. When going off-hook, the modem 301 turns on the off-hook output terminal of the I / O 305 for NCU. The system-side chip 311 of the silicon DAA 317 instructs the line-side device 313 to perform an off-hook operation, and the line-side device 313 performs an off-hook operation.
[0015]
FIG. 2 is a flowchart of the off-hook detection process.
When instructed by the host 302 to start communication by the AT command, the modem 301 requests line voltage data from the silicon DAA 317 and obtains the data before performing an off-hook operation (FIG. 2: Step 2). If the data is equal to or less than a preset threshold value (FIG. 2: Step 3), it is determined that the attached telephone is in an off-hook state, and a "LINE IN USE" result code is output to the host to be attached. This indicates that the start of communication has been stopped while the telephone is off-hook (FIG. 2: Step 4). This result code may be different. If the voltage value is equal to or higher than the threshold value, dialing is started (FIG. 2: Step 5). When this is completed, the normal communication operation starts (FIG. 2: step 6).
[0016]
This threshold value is set in advance, but may be set externally by an S register (an internal register of the modem 301).
[0017]
【The invention's effect】
As described above, according to the present invention, in a communication device using a silicon DAA, it is possible to easily detect that an attached telephone is off-hook without separately providing an off-hook detection circuit for the attached telephone.
[Brief description of the drawings]
FIG. 1 is a configuration example diagram of a modem device using a silicon DAA.
FIG. 2 is a flowchart illustrating a processing procedure of the present invention.
FIG. 3 is an example diagram of an off-hook check circuit of an attached telephone.
[Explanation of symbols]
201 modem 202 telephone line 203 resistance (100Ω)
204 Varistor 205 Photocoupler 301 Modem 302 Host 303 DSP
304 Communication I / O
305 NCU I / O
306 Silicon DAA interface 307 ROM
308 RAM
309 Off hook signal 310 Ring signal 311 System side chip 312 Isolation barrier capacitor 313 Line side chip 314 Peripheral circuit 315 Line 1
316 line 2
317 Silicon DAA

Claims (2)

In a communication device connected to a telephone line and performing data communication, another telephone is provided along with the telephone line, and when a communication start instruction is issued from a host that controls the communication device, before a telephone goes off-hook, The DAA circuit for measuring the voltage of the telephone line and, if the measured value is equal to or less than a preset threshold value, recognizes that the external telephone connected in parallel to the same telephone line is in an off-hook state and starts communication. And a DSP for stopping the communication and notifying the host of the suspension. 2. The communication device according to claim 1, wherein the preset threshold value can be externally set as a parameter.

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