JP2012089970A - Facsimile device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a facsimile device which can determine the hook state of an external phone correctly by voltage detection even if the destination of a telephone line is changed and thereby the line voltage is changed.SOLUTION: A facsimile device 10 comprises a diode bridge 14 connected with a telephone line 3, a changeover switch 15 which changes over an external phone 4 between a connection route 1 connected to the pre-stage of the diode bridge 14 and a connection route 2 connected to the post-stage of the diode bridge 14, a silicon DAA 13 (a voltage detection unit 21) which detects a voltage applied to the external phone 4 from the telephone line 3, and a control unit 11 which controls the changeover switch 15 to change over the connection route 1 and the connection route 2, and performs change over determination processing for determining whether the external phone 4 is on-hook or off-hook from the comparison result of the line voltage detected on the connection route 1 by the voltage detection unit 21 and the line voltage detected on the connection route 2 by the voltage detection unit 21.

Description

  The present invention relates to a facsimile apparatus to which an external telephone is connected.

  When a telephone line is shared between a facsimile machine and another device such as an external telephone, the hook state of the external telephone connected in parallel with the facsimile machine detects the DC power supply for communication supplied from the exchange. Judging by doing.

  For example, in a facsimile machine using silicon DAA (Data Access Arrangement), a voltage detection unit (voltage detection circuit) built in silicon DAA (semiconductor DAA) is used for on-hook (standby) and off-hook (line acquisition). ) Is detected and determined. Specifically, a DC loop is formed between the external telephone and the exchange device, and when the off-hook current flows to the external telephone, the DC loop is opened and no current flows to the external telephone. A voltage drop occurs due to the internal resistance of the external telephone. Therefore, the line voltage during standby (steady state) detected by the silicon DAA is used as the line voltage during on-hook, and a determination voltage for determining off-hook is obtained from the line voltage during on-hook and stored as a preset value in advance. When the line voltage is monitored and falls below the determination voltage of the set value, it is determined to be in the off-hook state (see Patent Documents 1 to 3).

JP 2005-057659 A JP 2006-270742 A JP 2006-270743 A

  In general, the connection between the facsimile apparatus and the telephone line can be easily changed by the user by connecting / disconnecting a modular connector such as the RJ-11 type, and the facsimile apparatus is turned on or off. The connection destination of the exchange device can be changed regardless of whether it exists. In addition, the line voltage (DC voltage value) of the telephone line varies depending on the connected switching device, such as 48 Vdc for a public line and 24 Vdc for a private branch exchange.

  Since the off-hook determination voltage varies depending on the line voltage, it is necessary to set a set value for the off-hook determination voltage according to the line voltage. However, if the user changes the connection destination from the public line to the private branch exchange or vice versa, the line In the method in which the voltage changes and the change in the line voltage is detected using the above-described silicon DAA to determine the hook state of the external telephone, there may be a case where the determination cannot be made correctly. That is, since the facsimile machine cannot determine whether or not the connection destination of the telephone line has been changed, when the connection destination is changed, the hook state is correctly determined even using the off-hook determination voltage based on the setting value before the change. I can't do it. Details will be described below.

  9 and 10 show an off-hook determination method for an external telephone using a conventional facsimile apparatus. Facsimile devices detect the line voltage at the time of power-on or standby and periodically detect the line voltage with the voltage detector of the silicon DAA, and determine the voltage value when it is determined to be standby (on-hook of an external telephone). It is recognized as (line reference voltage), an off-hook determination voltage is obtained from this reference voltage, and a set value of the off-hook determination voltage is stored in advance in a nonvolatile memory. During standby, the line voltage is monitored, and when the line voltage becomes lower than the set off-hook determination voltage, it is recognized (determined) as an off-hook state.

  As described above, the line voltage (DC voltage value) varies depending on the switching apparatus to be connected, such as 48 Vdc when the connection destination of the telephone line is a public line and 24 Vdc when the private branch exchange is connected. Further, since a voltage drop for the line from the switching apparatus to the facsimile apparatus occurs, the line voltage detected by the facsimile apparatus is lower than the supply voltage (DC voltage source voltage) of the switching apparatus. Also, the internal resistance of the external telephone 4 varies depending on the model (for example, 50Ω or 300Ω), and the line voltage at the time of off-hook (when a DC loop is formed) varies according to the difference in internal resistance for each model. For this reason, the off-hook determination voltage cannot be uniquely determined from the line voltage detected on the facsimile apparatus side.

  Therefore, conventionally, the facsimile machine periodically detects the line voltage when the power is turned on or in standby, and recognizes the voltage value when it is determined as standby (on-hook of an external telephone) as the reference voltage at the time of on-hook. From the reference voltage, an appropriate off-hook determination voltage corresponding to the internal resistance of the external telephone is obtained.

  FIGS. 11A and 11B show examples of erroneous determination of the hook state of the external telephone when the connection destination of the telephone line is changed when the facsimile apparatus is on standby. FIGS. D) shows an example of erroneous determination of the hook state of the external telephone when the telephone line connection destination is changed when the facsimile apparatus is turned off.

  For example, in FIG. 11A, the facsimile apparatus is connected to a public line, the line voltage is 48 Vdc, and the off-hook determination voltage of the external telephone is set around 24 Vdc. In this case, if the telephone line is disconnected and the connection destination is changed to the private branch exchange when the facsimile apparatus is on standby, the line voltage drops to 24 Vdc. Here, although the external telephone is in the on-hook state, if the line voltage falls below the set-off-hook determination voltage, the facsimile apparatus erroneously determines that the external telephone is off-hook. In FIG. 11B, the facsimile apparatus is connected to the private branch exchange, the line voltage is 24 Vdc, and the off-hook determination voltage of the external telephone is set to a voltage value lower than the line voltage (for example, 12 Vdc). . In this case, if the telephone line is disconnected and the connection destination is changed to a public line when the facsimile apparatus is on standby, the line voltage rises to 48 Vdc. However, if the external telephone is in an off-hook state and the line voltage is maintained near 24 Vdc, the facsimile apparatus erroneously determines that the external telephone is on-hook. In these cases, while the telephone line is not connected, the line voltage becomes equal to or lower than the unconnected determination voltage, and it is determined that the line is not connected.

  In FIG. 11C, the facsimile apparatus is connected to the public line, the line voltage is 48 Vdc, and the off-hook determination voltage of the external telephone is set around 24 Vdc. In this case, if the telephone line is disconnected when the facsimile apparatus is turned off and the connection destination is changed to the private branch exchange, the line voltage drops to 24 Vdc when the facsimile apparatus is turned on. Here, although the external telephone is in the on-hook state, if the line voltage falls below the set-off-hook determination voltage, the facsimile apparatus erroneously determines that the external telephone is off-hook. In FIG. 11D, the facsimile apparatus is connected to the private branch exchange, the line voltage is 24 Vdc, and the off-hook determination voltage of the external telephone is set to a voltage value lower than the line voltage (for example, 12 Vdc). . In this case, if the telephone line is disconnected when the facsimile apparatus is turned off and the connection destination is changed to a public line, the line voltage rises to 48 Vdc when the facsimile apparatus is turned on. However, if the external telephone is in an off-hook state and the line voltage is maintained near 24 Vdc, the facsimile apparatus erroneously determines that the external telephone is on-hook. In these cases, while the facsimile apparatus is turned off, the apparatus recognizes that the apparatus is turned off and does not detect the line voltage.

  As a method of monitoring the usage status of the external telephone and correctly determining the hook state, as shown in FIG. 12, a current detection circuit using a photocoupler is connected between the telephone line and the external telephone. There is a method of determining a hook state by detecting a current. FIG. 13 shows an example of a current detection circuit using a photocoupler.

  Technical standards required when connecting a facsimile machine to a telephone line require that the resistance component between the telephone line and the external telephone be kept low. On the other hand, a current detection circuit using a photocoupler is not preferable because it has a resistance component equivalent to several tens of ohms and does not meet the requirements. In addition, the current detection circuit has a problem of increasing the mounting area of components and increasing costs.

  The present invention is intended to solve the above-described problem, and a facsimile device capable of correctly determining the hook state of an external telephone by voltage detection even when the connection destination of the telephone line is changed and the line voltage changes. The object is to provide a device.

  The gist of the present invention for achieving the object lies in the inventions of the following items.

[1] In a facsimile machine to which an external telephone is connected,
A diode bridge connected to the telephone line;
A switching unit that switches between a first connection state in which the external telephone is connected to the previous stage of the diode bridge and a second connection state that is connected to the subsequent stage of the diode bridge;
A voltage detector for detecting a voltage applied to the external telephone from the telephone line;
The switching unit is controlled to switch between the first connection state and the second connection state, and the first voltage detected by the voltage detection unit in the first connection state and the voltage in the second connection state A control unit for performing a switching determination process for determining whether the external telephone is on-hook or off-hook from a comparison result with the second voltage detected by the detection unit;
A facsimile machine characterized by comprising:

  In the above invention, when the external telephone is off-hook, it is connected to the front stage of the diode bridge in the first connection state, so that a voltage drop due to the diode bridge does not occur. In the second connection state, since it is connected to the subsequent stage of the diode bridge, a voltage drop due to the diode of the diode bridge occurs. For this reason, the difference arises in the 1st voltage detected in the 1st connection state, and the 2nd voltage detected in the 2nd connection state.

  In the case of on-hook, since the external telephone is open, no current flows through the telephone line, and no voltage drop due to the diode of the diode bridge occurs even in the second connection state. Therefore, there is no difference between the first voltage and the second voltage.

  As a result, from the comparison result between the first voltage detected by switching to the previous stage (first connection state) of the diode bridge and the second voltage detected by switching to the subsequent stage (second connection state) of the diode bridge, It is possible to correctly determine whether the attached telephone is on-hook or off-hook.

  In addition, since switching is performed between the front stage and the rear stage of the diode bridge connected to the telephone line, the external telephone is maintained connected to the telephone line even if this switching is performed. For example, when the hook state of an external telephone is detected by a change in voltage, it can also be detected by simply switching the external telephone from a disconnected state to a connected state. The call is disconnected from the telephone line, and the call is interrupted. However, with the above configuration, such a call disconnection does not occur.

[2] The control unit stores the voltage detected by the voltage detection unit in a memory as a line reference voltage when the determination result of the switching determination process is on-hook, and waits to be on-hook when off-hook. The facsimile apparatus according to [1], wherein the voltage detected by the voltage detection unit is sometimes stored in a memory as a line reference voltage.

  In the above invention, it is possible to correctly determine the on-hook of the external telephone and store the voltage detected at the time of the on-hook in the memory as the line reference voltage. The line reference voltage stored in the memory can be used to obtain a determination voltage (threshold value) for determining the hook state of the external telephone.

[3] The facsimile apparatus according to claim 2, wherein in the process of waiting for the on-hook state, the detection voltage of the voltage detection unit is monitored and it is determined that the on-hook state has been detected when the voltage rises.

  When on-hook, the external telephone is open, so no current flows through the telephone line and no voltage drop occurs. In the off-hook state, a current flows through the external telephone (telephone line), and a voltage drop occurs due to the internal resistance of the external telephone. For this reason, the detection voltage always increases when going from off-hook to on-hook, and in the above invention, it is determined that the detection voltage is on-hook when the detection voltage changes. Accordingly, on-hook can be determined without switching between the first connection state and the second connection state, and the number of switching operations can be suppressed.

[4] The control unit
Controlling the steady state of the switching unit to the first connection state;
The switching reference process is performed when the facsimile apparatus is turned on to store the line reference voltage in a memory;
When it is determined whether it is on-hook or off-hook after storing the line reference voltage, the first voltage detected in the first connection state is compared with the line reference voltage stored in the memory, and the difference is predetermined. [2] or wherein the switching determination process is not performed and the external telephone is determined to be on-hook, and the switching determination process is performed when not within the allowable range [2] or [3] The facsimile apparatus according to [3].

  While the power of the facsimile apparatus is turned off, the connection destination of the telephone line may be changed to change the line voltage, and the line reference voltage stored in the memory before the power is turned off cannot be trusted. Therefore, in the above invention, when the facsimile apparatus is turned on, the line reference voltage is updated by performing the switching determination process and storing the line reference voltage in the memory.

  When determining whether the line reference voltage is on-hook or off-hook after the line reference voltage is stored (when the facsimile apparatus is on standby), the steady state of the switching unit is controlled to the first connection state, and the first detected in the first connection state is detected. And the line reference voltage stored in the memory by performing the switching determination process when the facsimile apparatus is turned on. When the difference is within a predetermined allowable range, it is determined that the external telephone is on-hook without performing the switching determination process. In this case, since the switching unit is maintained in the first connection state that is a steady state, it is not necessary to switch to the second connection state. Further, when the above difference is not within a predetermined allowable range, it is possible to correctly determine whether this time is on-hook or off-hook by performing a switching determination process.

[5] The control unit can detect a connection state of the telephone line,
The facsimile apparatus according to [4], wherein the switching determination process is performed when connection of the telephone line is detected from an unconnected state of the telephone line.

  When the facsimile apparatus is first connected to the telephone line, the line reference voltage is not stored in the memory because the switching determination process has not been performed before that time. In addition, when the telephone line connection is canceled while the line reference voltage is stored in the memory by performing the switching determination process and the telephone line is reconnected from the unconnected state, the connection destination of the telephone line is changed. The line reference voltage stored in the memory before the reconnection is not reliable. Therefore, in the above invention, when the connection of the telephone line is detected from the unconnected state of the telephone line, a switching determination process is performed and the line reference voltage is stored in the memory. After connection to the telephone line, it is possible to correctly determine the hook state of the external telephone using the line reference voltage stored in the memory by performing this switching determination process.

[6] The voltage detector is configured to detect a voltage applied to the external telephone from the telephone line equivalently by detecting a line voltage at a subsequent stage of the diode bridge. [1] to [1] 5]. The facsimile apparatus according to any one of [5].

  In the above invention, when the external telephone is on-hook, no current flows, so the voltage at the front stage of the diode bridge (voltage applied to the external telephone from the telephone line) is equivalently detected by the line voltage at the rear stage of the diode bridge. Can do.

  In addition, when the external telephone is off-hook in the first connection state, current flows through the telephone line through the external telephone connected to the front stage of the diode bridge (DC loop formation), but no current flows through the diode bridge. There is no voltage drop due to the diode. Therefore, the detection of the line voltage at the subsequent stage of the diode bridge is the same as the detection of the voltage at the previous stage of the diode bridge. Voltage applied to the external telephone from the telephone line) can be detected equivalently.

  According to the facsimile apparatus of the present invention, even when the connection destination of the telephone line is changed and the line voltage changes, the hook state of the external telephone can be correctly determined by voltage detection.

1 is a block diagram showing a schematic configuration of a facsimile apparatus according to an embodiment of the present invention. It is a figure explaining the off-hook determination operation | movement of the external telephone by a facsimile apparatus. It is a figure explaining the off-hook determination operation | movement of the external telephone by a facsimile apparatus. It is a figure explaining the on-hook determination operation | movement of the external telephone by a facsimile apparatus. It is a figure explaining the on-hook determination operation | movement of the external telephone by a facsimile apparatus. It is a flowchart which shows the control which the control part of a facsimile apparatus performs. It is a flowchart which shows the subroutine of the external telephone off-hook determination process in S103 of FIG. It is a figure explaining the example which determines the hook state of an external telephone correctly by the voltage detection in a facsimile apparatus. It is a figure explaining the off-hook determination method of the external telephone by the conventional facsimile apparatus. It is a figure explaining the off-hook determination method of the external telephone by the conventional facsimile apparatus. It is a figure explaining the example which erroneously determines the hook state of an external telephone by the voltage detection in the conventional facsimile apparatus. It is a block diagram which shows schematic structure of the conventional facsimile apparatus. It is a circuit diagram which shows an example of the current detection circuit using the conventional photocoupler.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration of a facsimile machine 10 according to an embodiment of the present invention. The facsimile apparatus 10 includes a control unit 11, a modem 12, a silicon DAA (Data Access Arrangement) 13, a diode bridge 14, a changeover switch 15, a disconnect switch 16, a telephone line connection connector 17, and an external telephone. A connection connector 18 and the like are provided.

  The control unit 11 is a circuit that performs overall control of the operation of the facsimile apparatus 10 and includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and a nonvolatile memory (not shown) as main parts. Is done. Although not shown, the control unit 11 includes a reading unit that reads an original image, a printer unit that forms and outputs an image corresponding to image data on a recording sheet, and various guidance information and operation states of the apparatus. An operation display unit for displaying or receiving various input operations from the user is connected.

  The telephone line connection connector 17 and the external telephone connection connector 18 are constituted by RJ-11 type modular connectors.

  The telephone line connection connector 17 is connected to the line side input / output of the silicon DAA 13 via the diode bridge 14. A modem 12 is connected to the system side input / output of the silicon DAA 13. One switching side contact a of the changeover switch 15 is connected to the preceding stage of the diode bridge 14, and the other switching side contact b of the changeover switch 15 is connected to the subsequent stage of the diode bridge 14. An external telephone connection connector 18 is connected to a terminal c of the changeover switch 15 via a disconnect switch 16.

  A public line or a private branch exchange is connected to the telephone line connection connector 17 (LINE) via the telephone line 3, and the external telephone 4 is connected to the external telephone connection connector 18 (TEL). ing.

  The diode bridge 14 functions to rectify the DC loop current from the telephone line 3 by the four diodes 20. The silicon DAA 13 includes a DC voltage detection unit 21 and a call signal detection unit (not shown), and performs functions such as call signal detection and line voltage detection. Since the voltage detector 21 of the silicon DAA 13 is DC-compatible, a rectifier circuit (diode bridge) for converting AC input from the telephone line 3 into DC input is required. Here, the silicon DAA 13 is connected to the rear stage side of the diode bridge 14. Thus, a separate rectifier circuit is unnecessary. In addition, this configuration uses the DC voltage detector 21 built in the silicon DAA 13.

  The changeover switch 15 functions to switch the connection destination of the external telephone 4 between the front side (contact a side) and the rear side (contact b side) of the diode bridge 14. Here, a path where the external telephone 4 is connected to the front side of the diode bridge 14 is a connection path 1, and a path where the external telephone 4 is connected to the rear stage is a connection path 2. The disconnect switch 16 is inserted in series in one of the two lines connecting the contact a side of the change-over switch 15 (the front side of the diode bridge 15) and the external telephone connector 18 and is connected to the external switch. The telephone 4 and the telephone line 3 are connected and disconnected.

  During standby, the coils of the changeover switch 15 and the separation switch 16 are in a non-energized state (steady state), and the telephone line 3 and the external telephone 4 in the deenergized state switch the changeover switch 15 and the separation switch 16. It is designed to be connected via During facsimile communication, the coil of the disconnect switch 16 is energized, and the telephone line 3 and the external telephone 4 are disconnected in the energized state. Further, the change-over switch 15 switches the connection destination of the external telephone 4 to the previous stage side (contact point a side / connection path 1 side) of the diode bridge 14 in the non-energized state and switches the connection destination of the external telephone 4 in the energized state. Switching to the rear side of the diode bridge 14 (contact b side / connection path 2 side) is performed.

  The voltage detection unit 21 of the silicon DAA 13 switches the voltage when the external telephone 4 is connected to the front stage of the diode bridge 14 (the line voltage of the connection path 1) and the subsequent stage of the diode bridge 14 by the switching by the changeover switch 15. The voltage (line voltage of the connection path 2) when connected to is respectively detected.

  Further, the control unit 11 monitors the detection voltage of the connection path 1 (steady state) by the voltage detection unit 21 of the silicon DAA 13, and the telephone line 3 is not connected if it is less than a predetermined determination voltage (unconnected determination voltage). When the voltage is equal to or higher than a predetermined determination voltage, it is determined that the telephone line 3 is connected.

  Next, the operation of the facsimile machine 10 will be described.

  FIG. 2 is a diagram for explaining the off-hook determination operation of the external telephone 4. When the external telephone 4 is off-hook, a direct current loop is formed between the external telephone 4 and the exchange device, and a current flows through the telephone line 3 and the external telephone 4. In the connection path 1 configured when the changeover switch 15 is in a steady state, the external telephone 4 is connected to the front stage of the diode bridge 14 and the “equivalent circuit in the case of the connection path 1” shown in the upper side of FIG. The When the line voltage is detected by the voltage detector 21 of the silicon DAA 13, a voltage value (V1) corresponding to the internal resistance of the external telephone 4 is detected. In this case, a voltage drop due to the diode bridge 14 does not occur.

  In the connection path 2 configured when the change-over switch 15 is switched from the steady state, the external telephone 4 is connected to the subsequent stage of the diode bridge 14, and “an equivalent circuit in the case of the connection path 2” shown on the lower side of FIG. Is configured. When the line voltage is detected by the voltage detector 21 of the silicon DAA 13, a voltage drop is generated by the diode 20 of the diode bridge 14, and a voltage value (V 2) obtained by subtracting the voltage drop due to the diode 20 from the voltage value (V 1) is obtained. Detected.

  As described above, when the external telephone 4 is off-hook, a difference between the voltage value detected by the connection path 1 and the voltage value detected by the connection path 2 is equal to the voltage drop due to the diode 20 of the diode bridge 14. If this voltage difference is not less than the specified range, it is determined that the external telephone 4 is in an off-hook state.

  The specified range of the voltage difference is determined based on the voltage drop amount of the diode 20 in the diode bridge 14, and the set value is stored in advance in a nonvolatile memory. For example, it may be 0.8V.

  As a result, as shown in FIG. 3, for example, when the external telephone 4 is in an off-hook state when the facsimile apparatus 10 is turned on, the changeover switch 15 is switched to the connection path 2 side to determine whether the external telephone 4 is on-hook or off-hook. If a voltage drop is detected, it can be determined that the device is in an off-hook state. Further, the line voltage is monitored by switching the changeover switch 15 to the connection path 1 side, and it can be determined that the on-hook state has been changed from the off-hook state when the rise is changed.

  FIG. 4 is a diagram for explaining the on-hook determination operation of the external telephone 4. When the external telephone 4 is on-hook, since the external telephone 4 is open, no current flows through the telephone line 3, and no voltage drop due to the diode 20 of the diode bridge 14 occurs even in the connection path 2. Therefore, by switching the changeover switch 15, the voltage value detected in the connection path 1 (“equivalent circuit in the case of the connection path 1” shown on the upper side of FIG. 4) and the connection path 2 ( There is no difference in the voltage value detected in the “equivalent circuit for path 2”). Even if a voltage difference occurs due to an error or the like, if the voltage difference is within a specified range, it is determined that the external telephone 4 is in an on-hook state.

  As a result, as shown in FIG. 5, for example, when the facsimile apparatus 10 is on standby, the telephone line 3 is switched from the public line to the private branch exchange, and the supply voltage (DC voltage source voltage) drops from 48 Vdc to 24 Vdc. Whether the attached telephone 4 is on-hook or off-hook can be determined to be in the on-hook state if the voltage drop is not detected when the changeover switch 15 is switched to the connection path 2 side.

  6 and 7 show the flow of control performed by the control unit 11 of the facsimile apparatus 10. The control unit 11 periodically repeats this control. For example, it is repeated at a predetermined time interval such as 2 ms or 10 ms.

  The controller 11 immediately after the power of the facsimile apparatus 10 is turned on, during initialization processing after the power is turned on, or when a change from unconnected to connected telephone line 3 is detected (step S101; Yes). Then, the external telephone off-hook determination process is performed in a subroutine (step S103).

  In the external telephone off-hook determination process shown in FIG. 7, the control unit 11 sets the changeover switch 15 to the non-energized state and sets the connection path 1 (step S201), and the voltage detection unit 21 of the silicon DAA 13 sets the line voltage. It detects (step S202). Subsequently, the changeover switch 15 is energized and set to the connection path 2 (step S203), and the line voltage is detected by the voltage detector 21 of the silicon DAA 13 (step S204).

  The line voltage in the connection path 1 and the line voltage in the connection path 2 are compared to determine whether or not the voltage difference is within a specified range (step S205).

  When the voltage difference is within the specified range (step S205; Yes), the control unit 11 returns the changeover switch 15 to the non-energized state and sets the connection path 1 (step S206). It determines with it being on-hook (step S207, Return). When the voltage difference is not within the specified range (step S205; No), the control unit 11 returns the changeover switch 15 to the non-energized state and sets the connection path 1 (step S208), and the external telephone 4 is off-hook. (Step S209, Return).

  Returning to FIG. 6, if it is determined in the off-hook determination process in step S103 that the external telephone 4 is on-hook (step S104; No), the process proceeds to step S106. If it is determined that the external telephone 4 is off-hook (step S104; Yes), the control unit 11 detects the line voltage by the voltage detection unit 21 of the silicon DAA 13 and determines whether or not the line voltage has changed. Monitor (Step S105; No). When it is detected that there is a change in the line voltage (step S105; Yes), the process proceeds to step S106. This change is a rise in line voltage due to the external telephone 4 being put on hook.

  Subsequently, the control unit 11 determines whether or not the line voltage is within the voltage range of the on-hook determination (step S106). The on-hook determination voltage range may be a preset value (for example, 2 to 3 V) or may be determined from an actual line voltage value (for example, ± 5 to 20% of the actual line voltage value). You may do it.

  When the measured value of the line voltage is used, when the process proceeds from step S104 to step S106, the voltage range for on-hook determination is determined using the line voltage detected in the off-hook determination process of step S103. In this case, since the external telephone 4 is on-hook and the line voltage is basically the same between the connection path 1 and the connection path 2, any line voltage may be used. When the process proceeds from step S105 to step S106, the voltage range for on-hook determination is determined using the line voltage after the change (line voltage at the time of on-hook in the connection path 1).

  Note that the line voltage is detected (measured) by confirming that the external telephone 4 is on-hook by the off-hook determination process (see FIG. 7) in step S103 and the change in line voltage in step S105. This criterion is accurate. Therefore, the voltage range for on-hook determination can be set to a relatively narrow range as in the above example, and since the range is narrowed, it is possible to reliably determine on-hook within this range. Therefore, the off-hook determination process (determination of the hook state of the external telephone 4 by switching the changeover switch 15 and detecting the line voltage) is omitted. On the other hand, since it is not clear whether it is on-hook or off-hook outside the above range, off-hook determination processing is performed.

  In other words, the on-hook determination voltage range needs to be set to a certain voltage range, but the line voltage when the off-hook state is surely known is measured, so the certain range can be set. .

  When the line voltage is within the voltage range of the on-hook determination (step S106; Yes), the control unit 11 determines that there is no change in the line voltage, and ends this process. If the line voltage is outside the voltage range for on-hook determination (step S106; No), the control unit 11 determines that there is a change in the line voltage and stores the line voltage at the on-hook time (reference) stored in the nonvolatile memory. The set value of (voltage) is corrected (step S107), and this process is terminated.

  In the process when the facsimile apparatus 10 is first turned on or connected to the first telephone line, the set value of the line voltage at the time of on-hook is not stored in the nonvolatile memory. In this case, the process proceeds from step S106 to step S107. The detected line voltage is stored in the nonvolatile memory as the set value of the line voltage at the on-hook time.

  Further, when the facsimile apparatus 10 is on standby (when not in facsimile communication) (step S101; No), the control unit 11 sets the changeover switch 15 to the non-energized state and sets the connection path 1, and the voltage detection unit of the silicon DAA 13 The line voltage is detected by 21 and it is determined whether or not the line voltage is within the on-hook determination voltage range (step S102).

  If the line voltage is within the on-hook determination voltage range (step S102; Yes), it is determined that the external telephone 4 is on-hook (step S108), and the process is terminated.

  If the line voltage is outside the voltage range for on-hook determination (step S102; No), the process proceeds to step S103, and the above-described external telephone off-hook determination process is performed (see FIG. 7). If the detected line voltage is outside the on-hook determination voltage range, the external telephone 4 may not be on-hook, but only the line voltage is detected by switching the changeover switch 15 by the external telephone off-hook determination process. It is easy and reliable to know whether it is on-hook or off-hook.

  8A and 8B show examples of determination of the hook state of the external telephone 4 when the connection destination of the telephone line 3 is changed when the facsimile apparatus 10 is on standby, and FIG. (D) shows an example of determining the hook state of the external telephone 4 when the connection destination of the telephone line 3 is changed when the facsimile apparatus 10 is powered off.

  For example, as shown in FIG. 8A, it is assumed that the facsimile apparatus 10 is connected to a public line and has a line voltage of 48 Vdc, and the connection destination is changed to a private branch exchange during standby and the line voltage drops to 24 Vdc. In this case, if the changeover switch 15 is switched at the time of connection of the telephone line and the voltage drop of the line voltage is not detected, it is determined that the external telephone 4 is on-hook, and the set value of the line voltage at the time of on-hook is changed.

  Further, as shown in FIG. 8B, the facsimile apparatus 10 is connected to the private branch exchange and the line voltage is 24 Vdc, and the connection destination is changed to a public line during standby and the line voltage rises to 48 Vdc. Assume that the line voltage is maintained in the vicinity of 24 Vdc while the attached telephone 4 is in the off-hook state. In this case, if the voltage drop of the line voltage is detected by switching the changeover switch 15 when the telephone line is connected, it is determined that the external telephone 4 is off-hook. Thereafter, when an increase in line voltage is detected, it is determined to be on-hook, and the set value of the line voltage at the time of on-hook is changed.

  In the case of FIGS. 8A and 8B, when the telephone line is not connected, the line voltage is equal to or lower than the unconnected determination voltage, and it is determined that the line is not connected. When the telephone line is not connected, there is a possibility that the telephone line has been reconnected (highly likely) when it is reconnected. The hook state of the external telephone 4 is determined (switching determination process) by detecting the line voltage.

  As shown in FIG. 8C, when the facsimile apparatus 10 is connected to a public line and the line voltage is 48 Vdc, the connection destination is changed to a private branch exchange when the power is turned off, and the line voltage drops to 24 Vdc when the power is turned on. To do. In this case, if the changeover switch 15 is switched when the power is turned on and no line voltage drop is detected, it is determined that the external telephone 4 is on-hook, and the set value of the line voltage at on-hook is changed.

  Further, as shown in FIG. 8D, the facsimile apparatus 10 is connected to the private branch exchange and has a line voltage of 24 Vdc, the connection destination is changed to a public line when the power is turned off, and the line voltage rises to 48 Vdc when the power is turned on. Then, it is assumed that the line voltage is maintained around 24 Vdc while the external telephone 4 is in an off-hook state. In this case, the external telephone 4 is determined to be off-hook if the changeover switch 15 is switched when the power is turned on to detect a voltage drop in the line voltage. Thereafter, when an increase in line voltage is detected, it is determined to be on-hook, and the set value of the line voltage at the time of on-hook is changed.

  In the case of FIGS. 8C and 8D, while the facsimile apparatus 10 is turned off, it recognizes that the apparatus is turned off and does not detect the line voltage. When the facsimile apparatus 10 is turned on, the telephone line may be reconnected while the power is off. Therefore, the hook state of the external telephone 4 is determined (switched) by switching the switch 15 and detecting the line voltage. Determination process).

  As described above, in the facsimile apparatus 10 according to the present embodiment, the line voltage detected by switching to the previous stage (connection path 1) of the diode bridge 14 and the line detected by switching to the subsequent stage (connection path 2) of the diode bridge 14. From the comparison result with the voltage, it is possible to correctly determine whether the external telephone 4 is on-hook or off-hook. In addition, since switching is performed between the front stage and the rear stage of the diode bridge 14, the external telephone 4 is maintained connected to the telephone line 3 even if this switching is performed. For example, when the hook state of the external telephone 4 is detected by a change in voltage, it can be detected by simply switching the external telephone 4 between a state where it is disconnected from the telephone line 3 and a state where it is connected. The attached telephone 4 is disconnected from the telephone line 3 and the call is interrupted. However, such a call disconnection does not occur.

  The embodiment of the present invention has been described with reference to the drawings. However, the specific configuration is not limited to that shown in the embodiment, and there are changes and additions within the scope of the present invention. Are also included in the present invention.

  For example, the line voltage is detected using the voltage detector 21 built in the silicon DAA 13, but a separate voltage detector may be provided to detect the line voltage. Further, the voltage applied to the external telephone 4 from the telephone line 3 is detected equivalently by detecting the line voltage at the subsequent stage of the diode bridge 14, but the line voltage at the subsequent stage of the changeover switch 15 is detected. Thus, the voltage applied to the external telephone 4 from the telephone line 3 may be directly detected. When this voltage is detected by a DC voltage detector, the detection can be performed by providing a rectifier circuit between the voltage detector.

  In the process shown in FIG. 6, the external telephone off-hook determination process (step S103) is always performed when the facsimile apparatus 10 is turned on (including during the initialization process). You may be sure to do it.

  The on-hook voltage of the external telephone 4 may be detected by either the connection path 1 (first connection state) or the connection path 2 (second connection state). The changeover switch 15 (switching unit) may set the connection path 2 (second connection state) to a steady state. However, since a voltage drop occurs in the connection path 2 (second connection state) connected to the subsequent stage of the diode bridge 14, as described in the embodiment, the changeover switch 15 keeps the connection path 1 (first connection state) steady. It is preferable to be in a state.

  In the other embodiments, the facsimile apparatus has been described as an example. However, the present invention can be applied to other types of receiving apparatuses having a function of receiving data and voice through a telephone line.

3 ... telephone line 4 ... external telephone 10 ... facsimile machine 11 ... control unit 12 ... modem 13 ... silicon DAA
DESCRIPTION OF SYMBOLS 14 ... Diode bridge 15 ... Changeover switch 16 ... Disconnection switch 17 ... Telephone line connection connector 18 ... External telephone connection connector 20 ... Diode 21 ... Voltage detection part a ... Contact b ... Contact c ... Terminal

Claims (6)

In a facsimile machine to which an external telephone is connected,
A diode bridge connected to the telephone line;
A switching unit that switches between a first connection state in which the external telephone is connected to the previous stage of the diode bridge and a second connection state that is connected to the subsequent stage of the diode bridge;
A voltage detector for detecting a voltage applied to the external telephone from the telephone line;
The switching unit is controlled to switch between the first connection state and the second connection state, and the first voltage detected by the voltage detection unit in the first connection state and the voltage in the second connection state A control unit for performing a switching determination process for determining whether the external telephone is on-hook or off-hook from a comparison result with the second voltage detected by the detection unit;
A facsimile machine characterized by comprising: The control unit stores the voltage detected by the voltage detection unit in a memory as a line reference voltage when the determination result of the switching determination process is on-hook, and waits to be on-hook when off-hook and waits for the voltage when on-hook. The facsimile apparatus according to claim 1, wherein the voltage detected by the detection unit is stored in a memory as a line reference voltage. 3. The facsimile apparatus according to claim 2, wherein in the process of waiting for the on-hook operation, the detection voltage of the voltage detection unit is monitored and it is determined that the on-hook operation has occurred when the voltage rises. The controller is
Controlling the steady state of the switching unit to the first connection state;
The switching reference process is performed when the facsimile apparatus is turned on to store the line reference voltage in a memory;
When it is determined whether it is on-hook or off-hook after storing the line reference voltage, the first voltage detected in the first connection state is compared with the line reference voltage stored in the memory, and the difference is predetermined. The switching determination process is performed without performing the switching determination process when it is within the allowable range, and the switching determination process is performed when it is not within the allowable range. 3. The facsimile apparatus according to 3. The control unit is capable of detecting a connection state of the telephone line;
The facsimile apparatus according to claim 4, wherein the switching determination process is performed when connection of the telephone line is detected from an unconnected state of the telephone line. The voltage detection unit detects a voltage applied to the external telephone from the telephone line equivalently by detecting a line voltage in a subsequent stage of the diode bridge. The facsimile apparatus according to one.

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