JP4060677B2 - Modem equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the above-described 2 in a semiconductor DAA (Data Access Arrangement) composed of a primary side circuit connected to a circuit network and a secondary side circuit connected to the primary side circuit via an insulating circuit. When a DSP (Digital Signal Processor) that modulates and demodulates data is connected to the secondary circuit, a modem that can detect ringing and polarity reversal from the network without using the DSP even when the DSP is in an energy saving state. The present invention relates to an apparatus and a communication apparatus using the apparatus.
[0002]
[Prior art]
In recent years, with the spread of the Internet, digital mobile phones, and the like, communication devices such as mobile terminals and small terminals have been downsized.
[0003]
However, a communication device with a built-in modem connected to a public network requires a relatively large transformer for the purpose of DC insulation for connection to the network, and this transformer hinders downsizing of the communication device. It is a factor.
[0004]
However, with the advancement of progress and isolation technology of the recent semiconductor processing technology, semiconductor DAA performing network control or the like have been developed, extremely compact pulse transformer and capacitor the function of transformer, it is replaced by a photo-coupler or the like It has become possible (see Patent Document 1).
[0005]
Such functional elements formed of semiconductors are expected to reduce the size and cost of communication devices, and are being sought for use in communication devices that are not portable terminals such as facsimile devices.
[0006]
Such a communication apparatus requires a network control function for controlling the network, a modulation / demodulation function for performing modulation / demodulation of signals transmitted / received via the network.
[0007]
As described above, the network control function is made semiconductor by the semiconductor DAA, and the modulation / demodulation function is called a so-called modem. Today, a DSP formed by a semiconductor process is used as a main part to perform high-speed processing. Yes.
[0008]
Accordingly, both the network control function and the modulation / demodulation function, which are the minimum functions necessary for communication, are supplied as a semiconductor.
[0009]
[Patent Document 1]
Japanese Patent Laid-Open No. 06-098038
[Problems to be solved by the invention]
However, communication devices are strongly required to reduce power consumption from the viewpoint of environmental considerations, etc., and in order to respond to this, energy saving functions are becoming almost standard equipment. Since it is directly connected to the DSP of the modem device having the modulation / demodulation function, there is a problem that ringing and polarity reversal cannot be detected unless the same power as that in the normal state is supplied to the DSP even in the energy saving state.
[0011]
That is, the modem apparatus performs modulation / demodulation of data as described above, but it is necessary to perform modulation / demodulation processing at high speed from the viewpoint of increasing the amount of data to be handled. For this reason, a DSP in which a function responsible for modulation / demodulation is made into a semiconductor is used, and its operating frequency is high. As the operating frequency increases, the power consumption increases accordingly.
[0012]
On the other hand, in the energy saving state, the power supply to the minimum equipment necessary for reception is stopped or suppressed to reduce power consumption. However, the DSP is connected to the semiconductor DAA and detected by the semiconductor DAA. Since the ringing and polarity reversal are notified to the communication apparatus main body through the DSP, the power supply to the DSP must be supplied in the same manner as in the normal state even in the energy saving state.
[0013]
Therefore, since the semiconductor DAA is used, the power consumption is increased in the state where the same power is supplied to the DSP even during energy saving as compared with the case where the DSP is brought into the energy saving state without using the semiconductor DAA.
[0014]
SUMMARY OF THE INVENTION An object of the present invention is to provide a modem device capable of detecting ringing and polarity reversal without using a DSP at the time of energy saving so as to enhance the energy saving effect and a communication device using the modem device. And
[0015]
[Means for Solving the Problems]
In order to solve the above problems, the present invention comprises a primary circuit connected to a network and a secondary circuit connected to the primary circuit via an insulation circuit, and controls the network. And a periodic signal generator in a modem device that is connected to the secondary side circuit of the semiconductor DAA for transmitting / receiving data and performs modulation / demodulation of data to be transmitted / received, and connected to the communication device main body by a system bus. And a ring / polarity inversion detection circuit comprising a cycle detection unit and a cycle comparison unit, and the cycle signal generation unit has a pulse width corresponding to a half cycle of the signal based on a signal from the secondary side circuit. A half-period pulse signal is generated and output to the period detection unit, and the period detection unit detects the period of the half-cycle pulse signal. age Output to the cycle comparing section, if it can not detect the period, as the signal from the secondary circuit is a polarity inversion signal, the periodic comparison signal indicating a polarity inversion detection signal Output to the communication device main body without passing through a section, and the period comparison section stores the half period of the ringing signal as a reference period in advance, and compares the detection period from the period detection section with the reference period. If they match, it is determined that the signal from the secondary circuit is a ringing signal, and if they do not match, it is determined that the signal from the secondary circuit is noise and the communication device a and outputs to the main body, this ring polarity inversion detection circuit, when the power supply to the DSP is stopped or suppressed, whether the signal from the secondary circuit is a ringing signal polarity Detecting whether a is either noise is rolling signal, and outputs the detection result to the communication device main body.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a communication device using a modem device according to the present invention. Note that examples of such a communication apparatus include a facsimile machine, a personal computer, a portable terminal, and the like. In this embodiment, a facsimile machine will be described as an example.
[0018]
The facsimile apparatus includes a system control unit 11. A system bus 12 is connected to the system control unit 11, and a program ROM 13, a data RAM 14, an operation display unit 15, a reading unit 16, a recording unit 17, A clock unit 18 is connected, and a DSP 31 which is a main component of the modem device is connected via a DSP side interface 32.
[0019]
The DSP 31 is connected to the secondary circuit 35 of the semiconductor DAA, and the secondary circuit is connected to the primary circuit 22 via the insulation circuit 21. The primary circuit 22 is a capacitor circuit for line filters. 23 is connected to the line network.
[0020]
The line filter capacitor circuit 23 is composed of a capacitor connected to Tip (L1) and Ring (L2) to which the primary circuit 22 is connected. The line filter capacitor circuit 23 is provided in accordance with safety standards corresponding to the IEC60950 and UL1950 standards. Yes.
[0021]
The modem device 20 according to the present embodiment includes a DSP 31, a DSP side interface 32, a ring / polarity inversion detection circuit 33, a ring / polarity inversion detection circuit side interface 34, a secondary side circuit 35, and the like.
[0022]
The primary side circuit 22 operates by local power supply and performs data control with the secondary side circuit 35 to perform incoming call detection, network control such as call processing to the line network, and transmission / reception of transmission / reception data, It is formed by DAA by a semiconductor process.
[0023]
The insulating circuit 21 is composed of a pulse transformer, a capacitor, a photocoupler, and the like, and connects the line network and the secondary circuit 35 in a state of being galvanically insulated.
[0024]
The system control unit 11 controls each component while using the data RAM 14 as a work area according to a control program stored in the program ROM 13.
[0025]
The system control unit 11 is in an energy saving state such as power supply being suppressed during energy saving. If ringing or polarity reversal is detected at this time, the system control unit 11 including the system control unit 11 is in an energy saving state during energy saving. Can be controlled to return to the normal state.
[0026]
By the way, the energy saving state is a state in which the operation of devices other than the devices required during reception waiting such as ringing is stopped or suppressed, and the system control unit 11, the recording unit 17, the reading unit 16, and the operation display unit 15. The DSP 31, the system bus 12, the secondary circuit 35, and the like enter such an energy saving state, and at that time, power supply to the corresponding device is stopped or suppressed.
[0027]
As a method for suppressing power supply, for example, the current can be limited or the operating frequency can be lowered. When the operating frequency is changed, the frequency from the clock circuit in the clock unit 18 is lowered.
[0028]
The data RAM 14 temporarily stores the image information read by the reading unit 16 as a file until the image data read by the recording unit 17 is recorded by the recording unit 17. In addition, a buffer page memory (not shown) for developing raw data when storing and recording data is provided so that the memory contents are backed up by a backup circuit (not shown) and stored even when the apparatus is powered off. It has become.
[0029]
The operation display unit 15 includes a numeric keypad for designating a destination telephone number, a start key, a one-touch dial key, and various other keys. The operation display unit 15 includes a display such as a liquid crystal display device, and the operation status of the device to be notified to the user. Display various messages.
[0030]
The reading unit 16 is for obtaining image information by reading a document image at a predetermined reading line density such as 3.85 lines / mm, 7.7 lines / mm, and 15.4 lines / mm. Information is temporarily stored in a line buffer once and transferred to a required device.
[0031]
The recording unit 17 records and outputs the received image information in accordance with the linear density, and records and outputs the image information read by the reading unit 16 in accordance with the linear density (copy operation). Also used for management report output.
[0032]
The clock unit 18 includes a clock circuit that generates a predetermined clock signal and counts the current time. On the other hand, when the time constant set by the system control unit 11 counts down and times out, the system control unit 11 is timed out. Notification is performed and a timer operation is performed.
[0033]
The DSP 31 modulates and demodulates data to be transmitted and received at high speed. The DSP-side interface 32 serves as an interface between the DSP 31 and the system bus 12 during normal operation. The DSP 31 and the DSP-side interface 32 consume power when saving energy. The power supply is stopped or suppressed so as to be suppressed.
[0034]
The ring / polarity reversal detection circuit 33 operates normally during energy saving and detects ringing and polarity reversal that are energy-saving recovery factors. The ring / polarity reversal detection circuit side interface 34 detects the ring / polarity reversal when energy is saved. It serves as an interface for outputting a signal from the circuit 33 to the system control unit 11 via the dedicated line 24.
[0035]
Note that detection of ringing and polarity reversal in the normal state is performed by the secondary circuit 35, and the detection result is sent from the DSP 31 to the system control unit 11 via the system bus 12.
[0036]
Therefore, if the ring / polarity inversion detection circuit 33 and the ring / polarity inversion detection circuit side interface 34 are operated normally even during normal operation, the system control unit 11 receives the signal from the ring / polarity inversion detection circuit side interface 34 and the DSP. A situation occurs in which a signal from the side interface 32 is input in competition.
[0037]
In such a case, it is preferable that the system control unit 11 performs control so that only a signal from the DSP side interface 32 is captured.
[0038]
Of course, in the normal state, the operations of the ring / polarity inversion detection circuit 33 and the ring / polarity inversion detection circuit side interface 34 may be stopped. By doing so, there is an advantage that the control burden on the system control unit 11 is reduced.
[0039]
The secondary side circuit 35 enables transmission and reception data such as ringing and polarity reversal and transmission / reception data to be transmitted to and received from the DSP 31 and the primary side circuit 22, and the operating frequency is lowered in the energy saving state.
[0040]
As shown in FIG. 2, the ring / polarity inversion detection circuit 33 includes a periodic signal generation unit 41, a period detection unit 42, and a period comparison unit 43.
[0041]
When the ringing signal as shown in FIG. 3A is input to the secondary side circuit 35, the A signal and the B signal shown in FIG. 3B and FIG. 3C are output to the periodic signal generation unit 41. When a polarity inversion signal as shown in FIG. 4A is input, the A signal and B signal shown in FIGS. 4B and 4C are output to the periodic signal generator 41.
[0042]
The A signal is a one-pulse pulse signal that is output when the input signal is equal to or higher than a preset positive threshold value Vt, and the B signal is a negative threshold value that the input signal is set in advance. This is a one-pulse pulse signal output when the level becomes Vt or less.
[0043]
When such A signal and B signal are input, the periodic signal generation unit 41 generates an A + B signal by combining them (FIGS. 3D and 4D), and when the A + B signal rises. A half-cycle pulse signal that rises and then falls when the A + B signal rises is generated (FIGS. 3E and 4E).
[0044]
That is, a signal that rises when the absolute value of the signal from the secondary side circuit 35 becomes larger than a preset threshold value Vt and falls when it becomes larger next time is generated as a half-cycle pulse signal.
[0045]
Since the ringing signal is a periodic signal having a predetermined period, the A signal and the B signal are pulse signals having periodicity, and accordingly, the half-period pulse signal is also a pulse signal having periodicity.
[0046]
On the other hand, the polarity inversion signal is a one-pulse signal that is input by discharging the line filter capacitor circuit 23 when the polarity is inverted, the A signal becomes a one-pulse signal, and the B signal remains a low level signal. Thus, the half-cycle pulse signal rises at the same time as the A signal, and then falls when the communication is completed and the polarity inversion returns.
[0047]
Then, such a half cycle pulse signal is sent to the cycle detector 42, where the cycle is detected.
[0048]
At this time, when a ringing signal is input to the secondary side DAA, the half-period pulse signal input to the period detector 42 is a pulse signal having periodicity as shown in FIG. However, when a polarity inversion signal is input, the half-period pulse signal remains at a high level as shown in FIG.
[0049]
If the period cannot be detected, it is determined as a polarity inversion signal, and a signal indicating this is directly output to the ring / polarity inversion detection circuit side interface 34 via the line A shown in FIG.
[0050]
On the other hand, when the period can be detected, a signal indicating the period is sent to the period comparison unit 43 as a detection period. Since the period of the ringing signal (for example, 40 msec) is stored in advance in the period comparison unit 43 as a reference period, the reference period is compared with the detection period.
[0051]
As a result, when these periods coincide with each other, it is determined that the signal input via the network is a ringing signal, and a signal indicating that is output to the ring / polarity inversion detection circuit side interface 34.
[0052]
Incidentally, line noise and internal noise may be input from the secondary side circuit 35 to the ring / polarity inversion detection circuit 33. Such noise is generally not confused with the polarity inversion signal because of its short period, but it is feared that it will be confused with the ringing signal.
[0053]
Therefore, the period comparison unit 43 compares the reference period and the detection period to confirm whether or not the input signal is a ringing signal.
[0054]
As described above, it is possible to detect the ringing signal and the polarity inversion signal via the ring / polarity inversion detection circuit 33 even if the power supply to the DSP 31 is stopped or suppressed during energy saving.
[0055]
Upon receiving such a ringing signal or polarity inversion signal, the system control unit 11 performs control for returning from the energy saving state to the normal state, returns to the normal state, and performs an incoming call operation or the like.
[0056]
As described above, in the present invention, the ringing signal and the polarity inversion signal can be detected. However, in the case of normal communication, the ringing signal is input prior to the polarity inversion. If it can be detected, there will be no inconvenience even if the DSP 31 is in an energy saving state during energy saving.
[0057]
However, in the case of a subscriber line network with a dial-in function or a number display contract, which is an additional function of the subscriber line network, polarity inversion occurs prior to the ringing signal, so only the ringing signal is detected. If it is configured to return to energy saving, it may not be possible to support such services.
[0058]
That is, in the case of a subscriber line network with a dial-in function contract, it takes at least about 2 seconds from the first polarity reversal until the ringing signal is transmitted. In the case of a network, it takes at least about 1 second until the information receiving terminal activation signal, which is a signal in accordance with the ringing signal, is transmitted from the first polarity inversion.
[0059]
The waiting time from the polarity reversal to the closing of the DC loop, which is the arrival of the primary response signal, is defined as 6 seconds.
[0060]
Therefore, if only the ringing signal is detected, the subscriber line switch may not be able to recognize the primary response signal within the specified time, and the communication line network disconnection operation will be performed, making it impossible to start the communication operation. Occurs.
[0061]
In the present invention, in order to cope with such a case, the polarity inversion and ringing can be detected independently to improve reliability and convenience.
[0062]
Next, a second embodiment of the present invention will be described with reference to the drawings. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals and description thereof is omitted as appropriate.
[0063]
In the previous embodiment, when the polarity inversion signal is input to the periodic signal generation unit 41, the half-period pulse signal remains a high level as shown in FIG. It could not be detected.
[0064]
In such a case, the periodic signal generator 41 may output a signal having a pulse width longer than a half cycle of the ringing signal as a half cycle pulse signal. Then, the detection cycle of the half-cycle pulse signal is compared with the reference cycle, and when they match, it is determined as a ringing signal, and when the detection cycle is longer than the reference cycle, it is determined as a polarity inversion signal. To do.
[0065]
By doing so, it is not necessary to provide the line A shown in FIG. 2, and the cost can be reduced.
[0066]
Next, a third embodiment of the present invention will be described with reference to the drawings. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals and description thereof is omitted as appropriate.
[0067]
In each of the embodiments described so far, in order to detect a ringing signal and a polarity inversion signal at the time of energy saving, a half-cycle pulse signal having a pulse width corresponding to a half cycle of these signals is generated.
[0068]
In contrast, in the present embodiment, it is possible to determine whether the signal is a ringing signal or a polarity inversion from the continuity of the A signal input to the ring / polarity inversion detection circuit 33.
[0069]
That is, as shown in FIG. 3A, the ringing signal is a signal that periodically fluctuates over a certain period of time, so that the A signal becomes a periodic pulse signal as shown in FIG. Since the signal is a one-pulse signal, the A signal is a one-pulse signal.
[0070]
Therefore, whether the signal from the secondary circuit 35 is a ringing signal or a polarity inversion signal can be determined based on whether or not the A signal is a pulse signal that varies periodically over a predetermined time.
[0071]
However, as shown in FIG. 5, the ringing signal is a signal in which a 1-second periodic signal is sent at intervals of 2 seconds, and considering the presence of line noise and internal noise, the continuity determination time of the A signal is as follows. Is preferably about 1 second.
[0072]
As can be easily understood by comparing the A signal in FIG. 3B and FIG. 4B and the A + B signal in FIG. 3D and FIG. Since it is a continuous periodic signal and is a single signal in the case of a polarity inversion signal, it can be determined whether it is a ringing signal or a polarity inversion signal by determining whether it is a continuous signal or a single signal.
[0073]
With such a configuration, it is not necessary to provide the line A shown in FIG. 2, and the cost can be reduced.
[0074]
Next, a fourth embodiment of the present invention will be described with reference to the drawings. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals and description thereof is omitted as appropriate.
[0075]
In the previous embodiment, when the signal input from the secondary circuit 35 becomes a level equal to or higher than a preset positive threshold value Vt, a 1-pulse A signal is output, and the input signal is set in advance. In addition, one pulse of the B signal is output when the level becomes equal to or lower than the negative threshold value Vt.
[0076]
At this time, it is assumed that the signal input to the secondary circuit 35 is distorted or attenuated depending on the state of the network, and that there is a lot of network noise.
[0077]
For example, if the signal attenuates and its peak value becomes smaller and does not exceed the set threshold value Vt, the A signal and the B signal cannot be normally generated, so that the ringing signal and the polarity inversion cannot be detected.
[0078]
Therefore, in this embodiment, the threshold value can be changed to improve the reliability.
[0079]
The threshold value is changed by inputting a threshold value change command from the operation display unit 15, and a user or a maintenance staff sets an optimum threshold value according to the state of the line network. This improves the reliability.
[0080]
Next, a fifth embodiment of the present invention will be described with reference to the drawings. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals and description thereof is omitted as appropriate.
[0081]
In each of the embodiments described so far, the DSP 31 and the system control unit 11 are connected by the DSP side interface 32, and the ring / polarity inversion detection circuit 33 and the system control unit 11 are connected by the ring / polarity inversion detection circuit side interface 34. It was the structure connected by.
[0082]
On the other hand, in this embodiment, as shown in FIG. 6, the functions of the DSP side interface 32 and the ring / polarity inversion detection circuit side interface 34 can be realized by one interface.
[0083]
That is, the DSP side interface 32 is used only in the normal state, and the ring / polarity inversion detection circuit side interface 34 is used only in the energy saving state, but both are similar in terms of circuits because they interface with the system control unit 11.
[0084]
Therefore, in the present invention, as shown in FIG. 6, a modem-side interface 36 having these functions is provided, and a signal switch 37 is provided.
[0085]
The signal switching unit 37 switches the connection so that the DSP 31 and the system control unit 11 can transmit and receive data in a normal state, and the ring / polarity inversion detection circuit 33 and the system control unit 11 perform data transmission during energy saving. Switch the connection so that you can send and receive.
[0086]
The specific configuration of the signal switch 37 can be formed by, for example, a relay switch. In this case, the relay is turned off in the normal state, the DSP 31 and the system control unit 11 are connected, and in the energy saving state. The relay is turned on, and the ring / polarity inversion detection circuit 33 and the system control unit 11 are controlled to be connected.
[0087]
As a result, only two interfaces are required, so that the cost can be reduced.
[0088]
【The invention's effect】
As described above, according to the present invention, the DSP 31 that modulates and demodulates data to be transmitted and received, the secondary circuit that is connected to the DSP 31 and controls the network, and the secondary circuit is connected. When the power supply to the DSP 31 is stopped or suppressed, a modem is connected with a ring / polarity inversion detection circuit that detects ringing and polarity inversion based on a signal from the secondary circuit and outputs the detected signal via a dedicated line. Since the apparatus is configured, it is possible to detect ringing and polarity reversal even when power supply to the DSP 31 is stopped or suppressed, and it is possible to effectively reduce power consumption during energy saving.
[Brief description of the drawings]
FIG. 1 is a block diagram of a communication device applied to the description of first to third embodiments of the present invention.
FIG. 2 is a block diagram of a ring / polarity inversion detection circuit;
FIG. 3 is a diagram illustrating a waveform of a ringing signal in a ring / polarity inversion detection circuit or the like.
FIG. 4 is a diagram illustrating a waveform of a polarity inversion signal in a ring / polarity inversion detection circuit or the like.
FIG. 5 is a diagram illustrating a waveform of a ringing signal.
FIG. 6 is a block diagram of a communication apparatus applied to the description of the fourth embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 System control part 12 System bus 15 Operation display part 18 Clock part 21 Isolation circuit 22 Primary side circuit 23 Line filter capacitor circuit 24 Dedicated line 31 DSP
32 DSP side interface 33 Ring / polarity inversion detection circuit 34 Ring / polarity inversion detection circuit side interface 35 Secondary side circuit 36 interface 37 Signal switch 41 Periodic signal generator 42 Period detector 43 Period comparator

Claims (6)

The semiconductor DAA 2 includes a primary circuit connected to a network and a secondary circuit connected to the primary circuit via an insulating circuit, and controls the network and transmits / receives data. In a modem device which is connected to a communication device main body and used by a system bus, and has a DSP which modulates and demodulates data to be transmitted / received by being connected to a secondary circuit,
A ring / polarity inversion detection circuit comprising a periodic signal generator, a period detector, and a period comparator,
The periodic signal generation unit generates a half cycle pulse signal having a pulse width corresponding to a half cycle of the signal based on the signal from the secondary side circuit, and outputs the signal to the cycle detection unit.
The cycle detection unit detects the cycle of the half cycle pulse signal, and when the cycle is detected, outputs the cycle as a detection cycle to the cycle comparison unit, and the cycle cannot be detected. In this case, assuming that the signal from the secondary side circuit is a polarity inversion signal, a signal indicating that is output as a polarity inversion detection signal to the communication device main body without passing through the period comparison unit,
The cycle comparison unit stores a half cycle of the ringing signal as a reference cycle in advance, compares the detection cycle from the cycle detection unit with the reference cycle, and if they match, the secondary side It is determined that the signal from the circuit is a ringing signal, and if it does not match, the signal from the secondary circuit is determined to be noise and is output to the communication device body side,
When the power supply to the DSP is stopped or suppressed by the ring / polarity inversion detection circuit, it is determined whether the signal from the secondary side circuit is a ringing signal, a polarity inversion signal, or noise. A modem device that detects and outputs the detection result to the communication device main body .   When the ring / polarity reversal detection circuit detects ringing or polarity reversal based on a signal from the secondary circuit and outputs the detection result, the ring / polarity reversal detection circuit passes through a dedicated line provided independently of the system bus. 2. The modem device according to claim 1, wherein the modem device outputs the data.   When the periodic signal generation unit generates and outputs a half-period pulse signal having a pulse width corresponding to a half period of the signal based on the signal from the secondary-side circuit, the signal from the secondary-side circuit The half-period pulse signal is generated so as to rise when the absolute value of becomes larger than a preset threshold value and then falls when it becomes larger next, and the threshold value can be changed. The modem device according to claim 1 or 2.   The ring / polarity inversion detection circuit detects whether the signal from the secondary side circuit is a continuous signal or a single signal that is continuous for a predetermined time, and in the case of a continuous signal, the secondary side The signal from the circuit is determined to be a ringing signal, and in the case of a single-shot signal, the signal from the secondary circuit is determined to be a polarity inversion signal. The modem device described. A DSP-side interface that enables the DSP to communicate with the communication device body via the system bus;
5. The ring / polarity reversal detection circuit side interface that enables the ring / polarity reversal detection circuit to communicate with the communication device main body via the dedicated line. Modem equipment. A modem-side interface that enables the DSP and the ring / polarity reversal detection circuit to communicate with the communication device body;
When appropriate power is supplied to the DSP, the DSP and the modem-side interface are connected so that the DSP can communicate with the communication device main body via the modem-side interface, and the DSP is connected to the DSP. When power supply is stopped or suppressed, the ring / polarity reversal detection circuit and the modem-side interface are connected so that the ring / polarity reversal detection circuit can communicate with the communication device body via the modem-side interface. The modem device according to claim 1, further comprising a signal switch to be connected.