Downsized facsimile machine using semiconductor DAA

A facsimile machine having a semiconductor DAA provided in a line I/F part performing facsimile data communication with a network includes a tone signal reception part in the form of a semiconductor device. The tone signal reception part is provided in the semiconductor DAA and receives a tone signal with high impedance through a path different from a path for receiving the facsimile data. The tone signal is supplied from the network or a downstream device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to facsimile machines, and more particularly to a facsimile machine including a data access arrangement (DAA) in the form of a semiconductor device (hereinafter referred to as a semiconductor DAA) and having an automatic switching function from telephone to facsimile (hereinafter also referred to as TEL→FAX) based on detection of a calling tone signal. (CNG signal), a facsimile communication network service function based on detection of a facsimile communication network signal (FCC signal), and a TEL→FAX remote switching function based on detection of a dual tone multi-frequency signal (DTMF signal).

2. Description of the Related Art

The conventional facsimile machine as disclosed in Japanese Laid-Open Patent Application No. 5-122428 or No. 8-139886, in order to establish interface (I/F) with a telephone line (line I/F), employs two transformers: one terminated by 600 Ω for impedance consistency between a FAX modem and the telephone line and for insulation between an integrated circuit on the network side and an integrated circuit on the modem side, and the other terminated by high impedance for transmission and insulation between the integrated circuit on the network side and the integrated circuit on the modem side with respect to the CNG signal, the FCC signal, and the DTMF signal that are tone signals.

On the other hand, recently, the semiconductor DAA, which realizes the analog circuit of the line I/F in the form of a semiconductor device without using transformers, has been used as an interface for a data modem, thus realizing circuit simplification and reduction in circuit size and cost.

The semiconductor DAA (hereinafter referred to as a silicon DAA) may be used in a facsimile machine as shown inFIG. 1. InFIG. 1, a line I/F part11is established between a network2and a modem12. The line I/F part11includes the silicon DAA, that is, an integrated circuit113on the network side, a reception and transmission part114, and an integrated circuit115on the modem and main control part side. The line I/F part11further includes a CML (Connect MODEM to Line) relay110, a diode bridge (full-wave rectifier circuit)111, a hook switch112, and a hook detector circuit116.

In the case of using the silicon DAA in the facsimile machine, it is additionally required to perform-detection of the CNG signal as the TEL→FAX automatic switching function, detection of the FCC signal as a call signal in the FAX communication network service, and detection of the DTMF signal as the TEL→FAX remote switching function. The silicon DAA, however, does not include a part receiving and transmitting these tone signals. Therefore, it is required, as conventionally, to provide a transformer118terminated by high impedance outside the silicon DAA.

SUMMARY OF THE INVENTION

Accordingly, it is a general object of the present invention to provide a facsimile machine in which the above-described disadvantage is eliminated.

A more specific object of the present invention is to provide a facsimile machine that uses a silicon DAA in a line I/F part for detecting a CNG signal indicating TEL→FAX automatic switching, an FCC signal as the call signal of the facsimile communication network service, and a DTMF signal for TEL→FAX remote switching instead of using a transformer terminated by high impedance for detecting those signals, thereby realizing simplicity in configuration, downsizing, and cost reduction.

The above objects of the present invention are achieved by a facsimile machine having a semiconductor DAA provided in a line I/F part performing facsimile data communication with a network, the facsimile machine including a tone signal reception part in the form of a semiconductor device, the tone signal reception part being provided in the semiconductor DAA and receiving a tone signal with high impedance through a path different from a path for receiving the facsimile data, the tone signal being supplied from the network or a downstream device.

According to the above-described facsimile machine, the semiconductor DAA includes the tone signal reception part that does not use a transformer to detect the tone signal. Therefore, the facsimile machine of the present invention can be reduced in size and cost.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will now be given, with reference to the accompanying drawings, of an embodiment of the present invention.

InFIGS. 2 through 8, the same elements as those ofFIG. 1are referred to by the same numerals.

FIG. 2is a block diagram showing the overall structure of a facsimile machine1according to the present invention. The facsimile machine1includes a main control part10, the line I/F part11, the modem12, a ROM13, a RAM14, an image information memory15, an encoding and decoding part16, a reading part17, a recording part18, an operation part19, and a display part20.

The main control part10controls the entire facsimile machine1in accordance with a variety of control programs recorded in the ROM13. The main control part10controls the line I/F part11related directly to the present invention. The RAM14includes a variety of necessary data and a work area for controlling the entire facsimile machine1. The image information memory15stores received image information and image information to be transmitted. The encoding and decoding part16compresses the image information to be transmitted in accordance with a given encoding method such as the MH (Modified Huffman), MR (Modified Read), or MMR (Modified Modified Read) encoding method, and expands the received image information in accordance with a given decoding method such as the MH, MR, or MMR decoding method. The reading part17converts an original to be transmitted into image data in accordance with the line density of the original. The recording part18prints the received image information on a sheet of paper in accordance with a given line density such as 3.85 lines/mm, 7.7 lines/mm, or 15.4 lines/mm and outputs the printed image information. The operation part19includes a numeric keypad as dial keys, a start/stop key as an operation signal, and function keys for executing a variety of operations. Information on the keys is displayed and confirmed on the display part20including display devices such as a liquid crystal and LEDs.

The modem12modulates data to be transmitted via the line I/F part11to the network2, and demodulates data received via the line I/F part11from the network2. Further, the modem12includes tone detectors that detect, by internal digital filters, a variety of tone signals such as a CNG signal, an FCC signal, and a DTMF signal supplied from the line I/F part11. When a call is transmitted or received, the main control part10performs given control of the network2mainly through controlling a variety of switches of the line I/F part11. Further, a downstream device3such as an external telephone or a TAM (telephone answering machine) is connected to the line I/F part11. The line I/F part11corresponds to the silicon DAA of the present invention.

Next, a brief description will be given, with reference toFIG. 2, of the TEL→FAX automatic switching function, the facsimile communication network service function, and the TEL→FAX remote switching function of the facsimile machine1of the present invention.

The TEL→FAX automatic switching function is switched ON when a user selects an automatic switching mode as the reception mode by the operation part19. With the TEL→FAX automatic switching function being ON, when a ringing signal arrives from the network2, the downstream device3responds prior to the facsimile machine1. At this point, if the arriving communication is a telephone call, the facsimile machine1makes no response. However, if the arriving communication is facsimile transmission, the facsimile machine1automatically detects the CNG signal of 1100 Hz characteristic of facsimile transmission through the line I/F part11so as to switch the reception mode to facsimile communication (a facsimile mode).

The facsimile communication network service function is one of the services provided by public telephone companies With this function, when a call arrives from a facsimile communication network, the facsimile machine1can detect the FCC signal of 1300 Hz (no-ringing call signal) arriving via the line I/F part11from the network2, thereby instantaneously determining that the call is facsimile communication.

The TEL→FAX remote switching function is switched ON when the user selects a telephone mode as the reception mode by the operation part19. With the TEL→FAX remote switching function being ON, when a ringing signal arrives from the network2, only the downstream device3responds. When the receiver answers and thereafter it is determined from a monitoring sound from the network2that the arriving communication is a facsimile transmission, a given number of DTMF signals corresponding to a remote number are generated by dialing in order to switch the reception mode from the telephone mode to the facsimile mode. The facsimile machine1detects the DTMF signals through the line I/F part11, thereby switching the reception mode from the telephone mode to the facsimile mode.

FIGS. 3 and 4are block diagrams showing configurations of the line I/F part11using the silicon DAA of the present invention. The silicon DAA has main functions such as insulation between the line end or the line side and the modem side, hybrid networking, and ringing detection. The silicon DAA is composed of three parts: the integrated circuit113on the network (2) side, the integrated circuit115on the modem (12) and main control part (10) side, and the reception and transmission part114, which is an insulator part providing direct current insulation and communicating data and signals between the integrated circuits113and115.

In addition to the silicon DAA, the line I/F part11includes the CML relay110for TEL→FAX switching, the diode bridge (full-wave rectifier circuit)111, the hook switch112, the hook detector circuit116, and capacitors117aand117bfor cutting DC loop. The line I/F part11is connected via terminals L1and L2to the network2and via terminals T1and T2to the downstream device3.

The silicon DAA is of either one of two types. That is, the silicon DAA may have a CODEC (coder-decoder) performing analog-to-digital (A/D) conversion and digital-to-analog (D/A) conversion on facsimile data provided in the modem12or the integrated circuit115on the modem and main controller side, or in the integrated circuit113on the network side.

InFIG. 3, a CODEC1135is provided in the integrated circuit113on the network side, and generally, a capacitor of high insulation is employed for the insulation part114of digital communication. On the other hand, inFIG. 4, a CODEC120is provided in the modem2(or in the integrated circuit115on the modem and main control part side), and generally, a high-insulation device such as an analog photocoupler is employed for the insulation part114of analog communication.

The following description is given of the case ofFIG. 3, where the CODEC1135is provided in the integrated circuit113on the network side.

InFIG. 3, in a wait state, the CML relay110is switched ON to the downstream device3such as a telephone Once facsimile communication starts, the main control part10switches a CML relay control signal OFF so that the network2is detached from the downstream device3. The diode bridge111sets the polarity of the DC loop current of the network2to one direction. A highly pressure-resistant MOSFET is used for the hook switch112, which sets the modem12in an off-hook condition.

When facsimile communication is started, a hook switch control signal is generated from the main control part10to be supplied to the hook switch112through a control I/F1152of the integrated circuit115, an insulation I/F1150, the capacitor114b of the insulation part114, and an insulation I/F1136of the integrated circuit113, controlling the hook switch112to an ON state. The hook detector circuit116detects the off-hook of the downstream device3. When the downstream device3is set in an off-hook state, the DC loop current flows through the hook detector circuit116, so that a hook detection signal switches from H (high level) to L (low level). Thereby, the off-hook of the downstream device3is detected in the main control part10.

Next, a description will be given of the integrated circuit113on the network side. Power for the integrated circuit113is supplied from the network2and is rectified by the diode bridge111into a voltage of a constant polarity irrespective of the voltage polarity of the network2. When facsimile communication is started, the off-hook state is determined based on whether the DC loop current flows through a current sensor1130. When a ringing signal from the network2reaches a ring detector circuit1131, a ring detection signal is output therefrom, switched between H and L in the same cycle. The output ring detection signal is supplied to the main control part10via the insulation I/F1136, the capacitor104aof the insulation part114, the insulation I/F1150, and the control I/F1152. Thereby, the ring detection signal is detected by the main control part10.

A terminal resistor1132determines the terminal impedance of the network2. The specifications of the terminal resistor1132depend on the communication standards of each country. A hybrid network1133includes a two-to-four line converter circuit that separates facsimile data into transmission and reception data (data to be transmitted and data received), a canceller circuit that prevents the transmission data from passing through a reception path, and a filter circuit. A reception amplifier1134aand a transmission amplifier1134bperform gain adjustment on the reception and transmission data, respectively. The CODEC1135performs A/D conversion and D/A conversion on the reception data and the transmission data, respectively.

The insulation I/F1136of the integrated circuit113on the network side integrates a hook signal supplied from the current sensor1130, the ring detection signal supplied from the ring detector circuit1131, and the facsimile reception data supplied from the CODEC1135into serial data supplied to the capacitor114aof the insulation part114. Further, the insulation I/F1136separates a serial signal supplied from the capacitor114bof the insulation part114into the hook switch control signal supplied to the hook switch112, a tone switch control signal supplied to a tone switch1139, and the facsimile transmission data supplied to the CODEC1135.

Resistors1138aand1138beach have a high resistance so that impedance is high with respect to the network2and the downstream device3. A tone amplifier1137is a differential amplifier whose inputs are connected via the resistors1138aand1138b with the terminals L1and L2of the network2or the terminals T1and T2of the downstream device3and produces an output signal that is a function of the difference between the inputs. The tone amplifier1137and the resistors1138aand1138bform a tone signal reception part.

The tone switch1139, which is ON except for during facsimile communication, is switched OFF immediately when facsimile communication is started so as to block noise that may come from the downstream device3via the tone amplifier1137during facsimile communication. ON-OFF control of the tone switch1139is performed by the tone switch control signal supplied from the main control part10to the tone switch1139via the control I/F1152, the insulation I/F1150, the capacitor114bof the insulation part114, and the insulation I/F1136. The output of the tone amplifier1137is additionally input to the reception amplifier1134avia the tone switch1139.

As described above, the silicon DAA of the present invention receives the tone signal supplied from the network2or the downstream device3with high impedance by using a path different from the facsimile data reception path such as the hybrid network1133, that is, by using the tone signal reception part (the tone amplifier1137and the resistors1138aand1138b) that is realized as a semiconductor device without using a transformer. Therefore, the facsimile machine1using the silicon DAA of the present invention can be reduced in size and cost.

Further, the silicon DAA of the present invention includes the integrated circuit113on the network side, the integrated circuit115on the modem and main control part side, and the insulation part114coupling the integrated circuits113and115, and has the tone signal reception part (the tone amplifier1137and the resistors1138aand1138b) provided in the integrated circuit113on the network side. Therefore, the tone signal received in the tone signal reception part can be transmitted to the integrated circuit115on the modem and main control part side via the coupling insulation part114.

Next, a description will be given of the integrated circuit115on the modem side. Power is supplied from the main body of the facsimile machine1to the integrated circuit115. The insulation I/F1150of the integrated circuit115on the modem side has the function opposite to that of the insulation I/F1136of the integrated circuit113on the network side. That is, the insulation I/F1150separates the output signal of the capacitor114aof the insulation part114into the facsimile reception data to a TX/RX I/F1151and the detection signals to the control I/F1152, and integrates the facsimile transmission data supplied from the TX/RX I/F1151and the control signals supplied from the control I/F1152into a signal supplied to the capacitor114bof the insulation part114. The TX/RX I/F1151functions as interface with the modem12for the facsimile data, and the control I/F1152functions as interface with the main control part10. The tone signals of the CNG signal and the FCC signal are detected by the tone detector formed of a digital filter provided in the modem12, and the DTMF signal is detected by the DTMF detector formed of a digital filter provided in the modem12.

A description will be given, with reference toFIGS. 5 through 8, of the flow of signals especially in the line I/F11of the facsimile machine1having the above-described configuration.

First, inFIG. 5, at the time of receiving the CNG signal when the TEL→FAX automatic switching function is started, the CML relay110is ON, the hook switch112is OFF, the tone switch1139is ON, and the downstream device3is in the off-hook state. At this point, when the CNG signal arrives from the network2, the CNG signal flows to the modem12through the CML relay110, the capacitors117aand117b, the resistors1138aand1138b, the tone amplifier1137, the tone switch1139, the reception amplifier1134a, the CODEC1135, the insulation I/F1136, the capacitor114aof the insulation part114, the insulation I/F1150, and the TX/RX I/F1151as indicated by the broken arrow in the drawing. The double-dot chain line arrow indicates the path of the DC loop current.

The CNG signal transmitted to the modem12has its characteristic frequency of 1100 Hz detected by the digital filter provided in the modem12. Thereby, the arrival of the CNG signal is recognized. By detecting the arrival of the CNG signal, the CML relay110is switched OFF by the CML relay control signal, the hook switch112is switched ON by the hook switch control signal, and the tone switch1139is switched OFF by the tone switch control signal. Thereby, the facsimile data transmitted from the network2can be received.

Next, inFIG. 6, at the time of receiving the FCC signal as the call signal of the facsimile communication network service, the CML relay110is ON, the hook switch112is OFF, the tone switch1139is ON, and the downstream device3is in an on-hook wait state. The flow of the FCC signal at this time is the same as that of the CNG signal as indicated by the broken arrow in the drawing. The FCC signal transmitted to the modem12has its characteristic frequency of 1300 Hz detected by the digital filter provided in the modem12, and similarly, the CML relay110is switched OFF, the hook switch112is switched ON, and the tone switch1139is switched OFF. Thereby, the facsimile data transmitted from the network2can be received.

Next, inFIG. 7, at the time of receiving the DTMF signal as a remote number when the TEL→FAX remote switching function is in operation, the CML relay110is ON, the hook switch112is OFF, the tone switch1139is ON, and the downstream device3is in the off-hook state. At this point, the DTMF signal arriving from the downstream device3(for instance, an external telephone) is supplied to the modem12through the hook detector circuit116, the capacitors117aand117b, the resistors1138aand1138b, the tone amplifier1137, the tone switch1139, the reception amplifier1134a, the CODEC1135, the insulation I/F1136, the capacitor114aof the insulation part114, the insulation I/F1150, and the TX/RX I/F1151as indicated by the broken arrow in the drawing. The double-dot chain line arrow indicates the path of the DC loop current.

The DTMF signal transmitted to the modem12has its combinations of specific frequencies identified by the digital filter provided in the modem12, so that the DTMF signal is detected. Thereby, as in the case of the CNG signal, the CML relay110is switched OFF, the hook switch112is switched ON, and the tone switch1139is switched OFF, so that the facsimile data transmitted from the network2can be received.

As described above, in the silicon DAA that does not use a transformer, a high-impedance CNG signal reception part as an automatic switching function from telephone to facsimile, a high-impedance FCC signal reception part receiving the FCC signal as the call signal of the facsimile communication network service, and a high-impedance DTMF signal reception part as the remote switching function from telephone to facsimile are formed by the common tone signal reception part (the tone amplifier1137and the resistors1138aand1138b), which part is provided as a path different from the facsimile data reception path. Therefore, each tone signal can be detected securely, and the facsimile machine1of the present invention can be reduced in size and cost.

Further, each of the CNG signal, the FCC signal, and the DTMF signal received by the tone signal reception part is transmitted to the circuit part on the modem and main control part side via a transmission line of the capacitor114aof the insulation part114, which transmission line is also used for the facsimile data. Therefore, the configuration of the insulation part114can be simplified. Further, in addition to the insulation part114, the reception amplifier1134a, the CODEC1135, and the insulation I/F1136can be also used for the facsimile data. Therefore, the configuration of the facsimile machine1can be simplified.

Furthermore, the tone switch1139for switching ON and OFF the tone signal path of the tone signal reception part is provided, for instance, on the output side of the tone amplifier1137. Therefore, noise coming from the tone signal reception part can be blocked while the facsimile data is received, so that the facsimile communication performance can be maintained.

Moreover, the control signals to the control parts provided in the silicon DAA, such as the tone switch control signal for switching ON and OFF the tone signal path of the tone signal reception part (the tone switch1139) and the hook switch control signal for switching ON and OFF the hook switch112are transmitted from the integrated circuit115on the modem and main control part side to the integrated circuit113on the network side via a common transmission line also used for the facsimile data, that is, the capacitor114b, of the insulation part114. Therefore, the configuration of the insulation part114can be simplified.

Next, as a result of the detection of the tone signal such as the CNG signal, the facsimile data transmitted from the network2is received. With the CML relay110being OFF, the hook switch112being ON, and the tone switch1139being OFF, the facsimile reception data transmitted from the network2is supplied to the main body of the facsimile machine1via the diode bridge111, the current sensor1130and the hook switch112, the hybrid network1133, the reception amplifier1134a, the CODEC1135, the insulation I/F1136, the capacitor114aof the insulation part114, the insulation I/F1150, the TX/RX I/F1151, and the modem12as indicated by the broken line inFIG. 8.

On the other hand, the facsimile transmission data, with the CML relay110being OFF, the hook switch112being ON, and the tone switch1139being OFF, is transmitted to the network2via the modem12, the TX/RX I/F1151, the insulation I/F1150, the capacitor114bof the insulation part114, the insulation I/F1136, the CODEC1135, the transmission amplifier1134b, the hybrid network1133, the current sensor1130and the hook switch112, and the diode bridge111as indicated by the double-dot chain line arrow inFIG. 8.

The above description is given of the case where the CODEC1135is provided in the integrated circuit113on the network side as shown inFIG. 3, while the present invention is also applicable in the case where the CODEC120is provided in the modem12as shown inFIG. 4(or in the integrated circuit115on the modem and main control part side) as in the case ofFIG. 3.

In the case ofFIG. 4, since the CODEC120is provided in the modem12, the insulation part114performs analog transmission. Accordingly, analog photocouplers114a′ and114b′ are employed as the high insulation elements of the insulation part114, the integrated circuit113on the network side lacks the insulation I/F1136ofFIG. 3so that the reception amplifier1134adirectly receives and the transmission amplifier1134bdirectly transmits the data and signals, and a reception amplifier115aand a transmission amplifier115bare provided in the integrated circuit115on the modem and main control part side so as to receive and transmit the data and signals, respectively. The configuration ofFIG. 4is specifically different from that ofFIG. 3in the above-described respects.

However, the facsimile machine1can produce the same effects in the case of having the CODEC120provided in the modem12as shown inFIG. 4as in the case ofFIG. 3.

The present invention is not limited to the specifically disclosed embodiment, but variations and modifications may be made without departing from the scope of the present invention.

The present application is based on Japanese priority application No. 2001-238212 filed on Aug. 6, 2001, the entire contents of which are hereby incorporated by reference.