JP2022149237A - Communication terminal device - Google Patents

Abstract

To prevent an external telephone or a communication terminal device from being broken due to excessive current from a line.SOLUTION: A communication terminal device includes: a line terminal 111 connected to a line 104 for communication; a telephone terminal 112 connected to an external telephone 103; a relay 124 that is connected between the line terminal 111 and the telephone terminal 112 and switches between connection and disconnection between the external telephone 103 and the line 104; and a host unit 160 that causes the relay 124 to disconnect between the external telephone 103 and the line 104 when excessive current arrives from the line 104.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to communication terminal devices.

A conventional communication terminal device detects an excessive current from a line by comparing the current or voltage with a threshold when capturing the line with a silicon DAA (see, for example, Patent Document 1). .

JP 2013-211791 A

However, in the conventional detection method, when the line is seized by the external telephone, an excessive current from the line switches the external telephone, the circuit for detecting the hookup of the external telephone, or the connection state with the line. There is a possibility that the relay or the like may be damaged.

Accordingly, it is an object of one or more aspects of the present disclosure to prevent an external telephone or communication terminal device from being damaged by an excessive current from a line.

A communication terminal device according to an aspect of the present disclosure includes: a line terminal connected to a line for communication; a telephone terminal connected to an external telephone; connected between the line terminal and the telephone terminal; a switching unit for switching connection and disconnection between the external telephone and the line; and control for causing the switching unit to disconnect the external telephone and the line when an excessive current arrives from the line. and a part.

According to one or more aspects of the present disclosure, it is possible to prevent an external telephone or a communication terminal from being damaged by an excessive current from a line.

1 is a block diagram showing a communication system including communication terminal devices according to Embodiments 1 and 2; FIG. 3 is a block diagram schematically showing the configuration of a line control unit according to Embodiment 1; FIG. FIG. 4 is a schematic first circuit diagram for explaining the operation of a conventional line control unit; FIG. 10 is a schematic second circuit diagram for explaining the operation of a conventional line control unit; 4 is a schematic first circuit diagram for explaining the operation of a line control unit in Embodiment 1; FIG. FIG. 8 is a schematic second circuit diagram for explaining the operation of the line control unit according to the first embodiment; FIG. 9 is a schematic third circuit diagram for explaining the operation of the line control unit according to the first embodiment; FIG. 4 is a schematic circuit diagram for explaining that the resistance of components is increased by shunting the current from the line; FIG. 11 is a block diagram schematically showing the configuration of a line control unit according to Embodiment 2; FIG. 2 is a schematic circuit diagram for explaining currents flowing in the circuit; FIG. FIG. 4 is a schematic first circuit diagram showing an operation example when the mode of the communication terminal device is fax standby, telephone standby, or DRD mode, and the external telephone is hooked from on-hook to off-hook; FIG. 10 is a schematic second circuit diagram showing an operation example when the mode of the communication terminal device is fax standby, telephone standby, or DRD mode, and the external telephone is hooked from on-hook to off-hook; FIG. 11 is a schematic third circuit diagram showing an operation example when the mode of the communication terminal device is fax standby, telephone standby, or DRD mode, and the external telephone is hooked from on-hook to off-hook; FIG. 10 is a schematic fourth circuit diagram showing an operation example when the mode of the communication terminal device is fax standby, telephone standby, or DRD mode, and the external telephone is hooked from on-hook to off-hook; FIG. 12 is a schematic fifth circuit diagram showing an operation example when the mode of the communication terminal device is fax standby, telephone standby, or DRD mode, and the external telephone is turned off-hook from on-hook; FIG. 14 is a schematic sixth circuit diagram showing an operation example when the mode of the communication terminal device is fax standby, telephone standby, or DRD mode, and the external telephone is turned off-hook from on-hook; 1 is a schematic circuit diagram for explaining the relationship among exchange voltage, line voltage, exchange-side resistance, line current, silicon DAA current, external telephone current, and external telephone resistance; FIG. FIG. 2 is a first schematic diagram for explaining a method of calculating a resistance value of an exchange; FIG. 4 is a second schematic diagram for explaining the method of calculating the resistance value of the exchange; FIG. 4 is a third schematic diagram for explaining the method of calculating the resistance value of the exchange; FIG. 4 is a schematic first circuit diagram showing an operation example when the mode of the communication terminal device is telephone or facsimile standby and the external telephone is hooked from on-hook to off-hook; FIG. 10 is a schematic second circuit diagram showing an operation example when the mode of the communication terminal device is telephone or fax standby and the external telephone is turned off-hook from on-hook; FIG. 11 is a schematic third circuit diagram showing an operation example when the mode of the communication terminal device is telephone or facsimile standby and the external telephone is switched from on-hook to off-hook; FIG. 11 is a schematic fourth circuit diagram showing an operation example when the mode of the communication terminal device is telephone or facsimile standby and the external telephone is hooked from on-hook to off-hook; FIG. 11 is a schematic fifth circuit diagram showing an operation example when the mode of the communication terminal device is telephone or facsimile standby and the external telephone is hooked from on-hook to off-hook; FIG. 20 is a schematic sixth circuit diagram showing an operation example when the mode of the communication terminal device is telephone or facsimile standby and the external telephone is turned off-hook from on-hook; FIG. 4 is a schematic first circuit diagram showing an operation example when the mode of the communication terminal device is answering or fax standby and the external telephone is hooked from on-hook to off-hook; FIG. 10 is a schematic second circuit diagram showing an operation example when the mode of the communication terminal device is answering or fax standby and the external telephone is hooked from on-hook to off-hook; FIG. 10 is a schematic third circuit diagram showing an operation example when the mode of the communication terminal device is answering or fax standby and the external telephone is hooked from on-hook to off-hook; FIG. 12 is a schematic fourth circuit diagram showing an operation example when the mode of the communication terminal device is answering or fax waiting and the external telephone is hooked from on-hook to off-hook; FIG. 10 is a schematic fifth circuit diagram showing an operation example when the mode of the communication terminal device is answering or fax standby and the external telephone is hooked from on-hook to off-hook; FIG. 20 is a schematic sixth circuit diagram showing an operation example when the mode of the communication terminal device is answering or fax waiting and the external telephone is hooked from on-hook to off-hook; 2 is a block diagram showing an example of hardware configuration; FIG.

Embodiment 1.
FIG. 1 is a block diagram showing communication system 100 including communication terminal device 110 according to Embodiment 1. As shown in FIG.
Communication system 100 includes external telephone 103 and communication terminal device 110 .
The external telephone 103 is a telephone connected to the communication terminal device 110 from the outside of the communication terminal device 110 .

Communication terminal device 110 includes line terminal 111 , telephone terminal 112 , scanner section 113 , printing section 114 , and line control section 120 .

A line terminal 111 is a terminal for connecting to the line network 102 via the exchange 101 . The line terminal 111 is connected to the line control section 120 .

The telephone terminal 112 is a terminal for connecting the external telephone 103 of the communication terminal device 110 . The telephone terminal 112 is connected to the line control unit 120, and the external telephone 103 connected to the telephone terminal 112 can access the exchange 101 and the line network 102 via the line control unit 120 and the line terminal 111. can be done.

A scanner unit 113 reads an image from a document and generates image data representing the read image. The scanner section 113 is connected to the line control section 120 and the printing section 114 .
For example, when copying is performed in the communication terminal device 110, image data generated by the scanner unit 113 is given to the printing unit 114, and the printing unit 114 prints an image on a medium based on the image data. .
When the communication terminal device 110 performs facsimile communication, the image data generated by the scanner unit 113 is given to the line control unit 120, and the line control unit 120 transmits the image data via the line terminal 111. to exchange 101 and circuit network 102 .

A printing unit 114 prints an image on a medium based on the image data.
For example, when image data is sent by facsimile communication, the image data is given to the printing unit 114 via the line terminal 111 and the line control unit 120, and the printing unit 114 prints the image on the medium based on the image data. to print the image.

The line control unit 120 is a line control circuit that controls communication via the line network 102 .

FIG. 2 is a block diagram schematically showing the configuration of line control section 120 according to the first embodiment.
The line control unit 120 includes a communication control unit 130, a modem 140, an insulation transfer unit 121, a silicon DAA 150, a DC loop forming unit 122, a diode bridge 123, a relay 124, a relay drive circuit 125, and an excessive current. It comprises a detection unit 126 , an external telephone hookup detection unit 127 and a host unit 160 .

Communication control unit 130 controls communication with line 104 .
The communication control unit 130 includes a ring detection determination unit 131, a DC loop formation instruction unit 132, a DC loop formation determination unit 133, a line voltage acquisition unit 134, a line current acquisition unit 135, and a pseudo RBT (Ring Back Tone). A generation unit 136 and a FAX communication processing unit 137 are provided.

Ring detection/judgment section 131 detects a ring signal arriving from line 104 . For example, the ring detection/judgment unit 131 is connected to the modem 140, judges the ON time and OFF time of the ring signal arriving from the line 104, and judges whether or not the ring signal has arrived. Here, the line 104 is a line outside the line terminal 111 and includes the exchange 101 and the line network 102 in FIG. Communication takes place on the line 104 .

DC loop formation instruction section 132 is connected to modem 140 and instructs DC loop formation section 122 to form a DC loop with line 104 or to cancel a DC loop with line 104 .

DC loop forming determination unit 133 is connected to modem 140 and determines whether or not DC loop forming unit 122 has maintained the DC of line 104 . If a DC loop is formed by the DC loop formation unit 122, the line 104 is captured, so the DC loop formation determination unit 133 functions as a line capture detection unit.

The line voltage acquisition unit 134 is connected to the modem 140 and acquires the line voltage of the line 104 detected by the silicon DAA 150 .
The line current acquiring unit 135 is connected to the modem 140 and acquires the current flowing through the DC loop forming unit 122 as the line current that is the current flowing through the line 104 .

Pseudo RBT generator 136 is connected to modem 140 and generates a pseudo RBT, which is a tone resembling RBT. Pseudo RBT is a sound output to a user who has made a call to make the user feel as if he or she is calling.

The FAX communication processing unit 137 is connected to the modem 140 and exchanges FAX signals with the line 104 to perform facsimile communication.

Modem 140 converts a signal from line 104 into a signal that can be processed by communication control section 130 , and converts a signal from communication control section 130 into a signal that can be sent to line 104 . For example, the modem 140 converts between digital signals handled by the communication control unit 130 and analog signals transmitted and received on the line 104 .
Modem 140 has control I/F (InterFace) 141 and I/F 142 .

The control I/F 141 includes a ring detection determination unit 131, a DC loop formation instruction unit 132, a DC loop formation determination unit 133, a line voltage acquisition unit 134, a line current acquisition unit 135, a pseudo RBT generation unit 136, and a FAX. It is connected to the communication processing unit 137 and the I/F 142 and serves as an interface for exchanging signals between the communication control unit 130 and the modem 140 .

The I/F 142 is connected to the control I/F 141 and the insulation transfer section 121 and is an interface for exchanging signals between the modem 140 and the silicon DAA 150 .

Insulated transfer unit 121 is connected to I/F 142 of modem 140 and silicon DAA 150, and separates the primary side and secondary side of line 104 in terms of direct current.

The silicon DAA 150 is a transmitter/receiver unit between the line 104 and the modem 140 that transmits or receives signals. Silicon DAA 150 seizes line 104 by connecting to line 104 . Specifically, the DC loop forming unit 122 forms a DC loop with the line 104, the silicon DAA 150 captures the line 104, and the DC loop forming unit 122 cancels the DC loop with the line 104. This causes silicon DAA 150 to release line 104 .
The silicon DAA 150 has an I/F 151 , a ring detector 152 and a line voltage detector 153 .

I/F 151 is connected to insulation transfer section 121 , ring detection section 152 , line voltage detection section 153 , and DC loop formation section 122 .
I/F 151 is an interface for transmitting signals from line 104 to modem 140 and transmitting signals from modem 140 to line 104 .

Ring detector 152 is connected to I/F 151, AC input side A and AC input side B of diode bridge 123, line terminal 111, relay 124, line voltage detector 153, and excessive current detector 126. be done.
Ring detection section 152 is an interface for detecting a ring signal coming from line 104 and providing the ring signal to ring detection determination section 131 .

The line voltage detection unit 153 detects the voltage of the line terminal 111 in order to detect the line voltage, which is the voltage of the line 104 .

A DC loop forming unit 122 forms and cancels a DC loop with the line 104 . A state in which the DC loop is eliminated is a state in which no DC loop is formed.
For example, the DC loop forming unit 122 is connected to the I/F 151 of the silicon DAA 150, the + side of the diode bridge 123, the - side of the diode bridge 123, and the ground of the silicon DAA 150, and holds the DC of the line 104. , to form a DC loop with line 104 .

The diode bridge 123 matches the polarity of the direct current of the line 104 to the direct current loop forming section 122, and supplies a unidirectional direct current to the direct current loop forming section 122 even if the polarity of the line 104 is reversed.

Relay 124 is connected to line terminal 111 , telephone terminal 112 , and external telephone hookup detector 127 .
The relay 124 is a switching unit that is arranged between the line terminal 111 and the telephone terminal 112 and switches connection and disconnection between the line 104 and the external telephone 103 . When communication terminal device 110 is in a standby state, relay 124 connects telephone terminal 112 and line 104 so that the user can make a call using external telephone 103 . When the communication terminal device 110 performs facsimile communication, the relay 124 disconnects the telephone terminal 112 and the line 104 so that noise from the transmitter of the external telephone 103 is transmitted through the silicon DAA 150 to the modem 140. do not enter.
Also, the relay 124 is provided with a coil 124 a that operates the relay 124 , and the coil 124 a is connected to the power source 115 and a relay drive circuit 125 that drives the relay 124 .

The relay drive circuit 125 turns on or off the relay 124 according to instructions from the host section 160 .

Line terminal 111 is connected to line 104 and excessive current detector 126 . The line terminal 111 is an insertion port for a communication cable.
Telephone terminal 112 is connected to external telephone 103 and external telephone hookup detector 127 . The telephone terminal 112 is a cable outlet.

Excessive current detection unit 126 is arranged between line terminal 111 and relay 124 and detects that an excessive current exceeding a predetermined threshold has arrived from line 104 . Excessive current detection section 126 notifies host section 160 of the detection result.

The external telephone hookup detection unit 127 is arranged between the telephone terminal 112 and the relay 124, and detects the non-conducting state of the external telephone 103 when the current from the line 104 does not flow to the external telephone 103. It functions as an external telephone continuity detection unit that detects the continuity state of the external telephone 103 when a current from the line 104 is flowing through the external telephone 103 . Here, it is assumed that the conductive state is a state in which the external telephone 103 is off-hooked, and the non-conductive state is a state in which the external telephone 103 is on-hooked. Note that even when the external telephone 103 is on-hook, if the external telephone 103 responds to an incoming call from the line 104 by means of an answering machine function or the like, it becomes conductive.

In Embodiment 1, the external telephone hookup detector 127 operates on the direct current of the line 104 when the external telephone 103 is hooked up. Thereby, the external telephone hookup detection unit 127 detects that the external telephone 103 is off-hooked. External telephone hookup detection section 127 notifies host section 160 of the detection result.

Host unit 160 is a control unit that controls relay 124 . For example, the host section 160 is a control section that controls the relay 124 according to the detection result of the excessive current detection section 126 or the detection result of the external telephone hookup detection section 127 . Specifically, host section 160 causes relay 124 to disconnect external telephone 103 and line 104 when excessive current arrives from line 104 . Here, the host unit 160 determines that an excessive current has arrived based on the detection result of the excessive current detection unit 126 when the current from the line 104 is equal to or greater than a predetermined threshold value. Specifically, host section 160 determines that an excessive current has arrived when excessive current detection section 126 detects that the current from line 104 is equal to or greater than a predetermined threshold.
The host unit 160 includes an external telephone hookup determination unit 161 , a line overcurrent determination unit 162 and a relay control unit 163 .

The external telephone hookup determination unit 161 is connected to the external telephone hookup detection unit 127, monitors the output of the external telephone hookup detection unit 127 for a predetermined time, and determines whether the external telephone 103 is hooked up. to judge.

The line overcurrent determination unit 162 is connected to the overcurrent detection unit 126, monitors the output of the overcurrent detection unit 126, and determines whether an overcurrent has flowed through the line 104, in other words, whether the current from the line 104 is excessive. determine whether there is

The relay control unit 163 is connected to the relay driving circuit 125 and turns on or off the relay 124 according to the determination result of the line overcurrent determination unit 162 or the detection result of the external telephone hookup detection unit 127 .

Next, in Embodiment 1, the operation against excessive current from line 104 will be described.
First, FIGS. 3 and 4 are schematic circuit diagrams for explaining the operation of a conventional line control unit.
In the conventional line control section, the excessive current detection section 126 shown in FIG. 2 is not provided, and the line excessive current determination section 162 is not provided in the host section 160#.

FIG. 3 shows a conventional standby state of a line control unit.
Here, relay 124 is turned off, and external telephone 103 and line 104 are connected.

Then, as shown in FIG. 4, when the user hooks up the external telephone 103, a direct current from the line 104 flows through the photocoupler functioning as the external telephone hookup detector 127, and the external telephone hookup is performed. Determination unit 161 determines that external telephone 103 is off-hooked.

If excessive current arrives from line 104 in the state shown in FIG. 4, the photocoupler, relay 124, or external telephone 103 functioning as external telephone hookup detector 127 may fail.

5 to 7 are schematic circuit diagrams explaining the operation of line control section 120 according to the first embodiment.
In Embodiment 1, a photocoupler functioning as the excessive current detector 126 is added.
First, as shown in FIG. 5, when the line control unit 120 is in the standby state, the relay 124 is turned off, and the external telephone 103 and the line 104 are connected.

Next, as shown in FIG. 6, when the user hooks up the external telephone 103, a current from the line 104 flows through the photocoupler functioning as the external telephone hookup detector 127, and the external telephone The external telephone hookup determination unit 161 determines that 103 has been hooked up. A current from the line 104 also flows through the light-emitting side of the photocoupler functioning as the excessive current detector 126 .
As a result, a current flows through the light receiving side of the photocoupler functioning as the excessive current detection unit 126. When the line current exceeds a predetermined threshold value, for example, 200 mA, the light receiving side of the photocoupler is turned on.
Then, when the current from the line 104 reaches or exceeds the threshold value (200 mA in this case) for determining an excessive current, the voltage at L3 becomes 0 V, and the line excessive current determination unit 162 determines that an excessive current has arrived.

Then, when line overcurrent determination unit 162 determines that an overcurrent has arrived, relay control unit 163 causes current to flow through the base of the transistor that functions as relay drive circuit 125, as shown in FIG. , turns relay 124 on. As a result, the connection with the line 104 is cut off, and the photocoupler functioning as the external telephone hookup detector 127, the relay 124, and the external telephone 103 can be protected from excessive current.

Since an excessive current of the line 104 flows through the light-emitting side of the photocoupler functioning as the excessive current detector 126, a resistor 128 is provided in parallel with the photocoupler as shown in FIG. Dividing the current I into a current I1 on the resistor side and a current I2 on the light emitting side can increase the durability of the component.

The addition of the photocoupler functioning as the excessive current detector 126 does not reduce the quality of facsimile communication for the following reasons.
By providing a capacitor (not shown) in parallel with the photocoupler, the effect on the AC signal can be almost eliminated.
In addition, although the DC resistance increases slightly, it is considered to be negligible and the line standard can be satisfied.

As described above, according to Embodiment 1, by providing the excessive current detection unit 126 for detecting excessive current from the line 104, when an excessive current arrives, the external telephone 103, the external By disconnecting the telephone hookup detector 127 and the relay 124 from the line 104, these failures can be prevented.

Embodiment 2.
As shown in FIG. 1, communication system 200 in Embodiment 2 includes external telephone 103 and communication terminal device 210 .
External telephone 103 in the second embodiment is similar to external telephone 103 in the first embodiment.

As shown in FIG. 1, communication terminal device 210 according to the second embodiment includes line terminal 111 , telephone terminal 112 , scanner section 113 , printing section 114 and line control section 220 .
The line terminal 111, the telephone terminal 112, the scanner unit 113 and the printing unit 114 of the communication terminal device 210 according to the second embodiment are the same as the line terminal 111, the telephone terminal 112 and the scanner unit 113 of the communication terminal device 110 according to the first embodiment. and the same as the printing unit 114 .

FIG. 9 is a block diagram schematically showing the configuration of line control section 220 according to the second embodiment.
The line control unit 220 includes a communication control unit 230, a modem 140, an insulation transfer unit 121, a silicon DAA 150, a DC loop forming unit 122, a diode bridge 123, a relay 124, a relay drive circuit 125, and an external It comprises a telephone hookup detection unit 127 and a host unit 260 .

Modem 140, insulation transfer unit 121, silicon DAA 150, DC loop formation unit 122, diode bridge 123, relay 124, relay drive circuit 125, and external telephone hookup detection unit 127 of line control unit 220 in Embodiment 2 Modem 140, insulation transfer unit 121, silicon DAA 150, DC loop formation unit 122, diode bridge 123, relay 124, relay drive circuit 125, and external telephone hookup detection unit 127 of line control unit 120 in form 1. .
Note that the line control unit 220 according to the second embodiment does not include the excessive current detection unit 126 according to the first embodiment.

Communication control unit 230 controls communication with line 104 .
The communication control unit 230 includes a ring detection determination unit 131, a DC loop formation instruction unit 132, a DC loop formation determination unit 133, a line voltage acquisition unit 234, a line current acquisition unit 235, a pseudo RBT generation unit 136, It has a FAX communication processing section 137 , an exchange side resistance value calculation section 238 and an external telephone current calculation section 239 .
The ring detection determination unit 131, the DC loop formation instruction unit 132, the DC loop formation determination unit 133, the pseudo RBT generation unit 136, and the FAX communication processing unit 137 of the communication control unit 230 according to the second embodiment are the communication control units according to the first embodiment. It is the same as the ring detection determination section 131 , the DC loop formation instruction section 132 , the DC loop formation determination section 133 , the pseudo RBT generation section 136 and the FAX communication processing section 137 of the section 130 .

The line voltage acquisition unit 234 is connected to the modem 140 and acquires the line voltage of the line 104 detected by the silicon DAA 150 . The line voltage acquisition unit 234 supplies the acquired voltage to the switch side resistance value calculation unit 238 and the external telephone current calculation unit 239 . Since the exchange 101 is connected to the line terminal 111, the voltage obtained here can be said to be the voltage on the exchange 101 side.

In the second embodiment, in line voltage acquisition section 234 , external telephone hookup detection section 127 detects the non-conducting state of external telephone 103 , and relay 124 connects external telephone 103 and line 104 . In addition, when the DC loop forming unit 122 has eliminated the DC loop with the line 104 , the first voltage, which is the voltage of the line 104 , is acquired. Also, when the relay 124 disconnects the line 104 from the external telephone 103 and the DC loop forming unit 122 forms a DC loop with the line 104, the voltage of the line 104 is Get the line resistance voltage. Furthermore, in the line voltage acquisition unit 234, the external telephone hookup detection unit 127 detects the conduction state of the external telephone 103, the relay 124 connects the external telephone 103 and the line 104, and the direct current voltage is detected. A second voltage that is the voltage of the line 104 is obtained when the loop forming unit 122 forms a DC loop with the line 104 .

The line current acquiring unit 235 is connected to the modem 140 and acquires the current flowing through the DC loop forming unit 122 as the line current that is the current flowing through the line 104 . The line current acquisition unit 235 supplies the acquired line current to the exchange side resistance value calculation unit 238 and the external telephone current calculation unit 239 .

In the second embodiment, line current acquisition section 235 has relay 124 disconnecting external telephone 103 and line 104 and DC loop forming section 122 forming a DC loop with line 104. A first current is obtained, which is the current from the line 104 when the current is on. In line current acquisition section 235, external telephone hookup detection section 127 detects the conduction state of external telephone 103, relay 124 connects external telephone 103 and line 104, and DC A second current is obtained from the line 104 when the loop forming unit 122 forms a DC loop with the line 104 .

The switch side resistance value calculation unit 238 uses the line voltage from the line voltage acquisition unit 234 and the line current from the line current acquisition unit 235 to calculate the switch side resistance value that is the resistance on the switch 101 side.
Specifically, the switch-side resistance value calculator 238 calculates the switch-side resistance value, which is the resistance value on the switch 101 side, from the first voltage, the line resistance voltage, and the first current.

The external telephone current calculation unit 239 uses the line voltage from the line voltage acquisition unit 234 and the line current from the line current acquisition unit 235 to calculate the external telephone current, which is the current of the external telephone 103 . The external telephone current calculator 239 supplies the calculated external telephone current to the host unit 260 .
Specifically, from the first voltage, the second voltage, the line resistance voltage, the first current, the second current, and the switch-side resistance value, the external telephone current calculator 239 calculates: When the external telephone 103 is in a conductive state, the relay 124 connects the external telephone 103 and the line 104, and the DC loop forming section 122 forms a DC loop with the line 104, An external telephone current, which is the current flowing from the line 104 to the external telephone 103, is calculated.

The host unit 260 uses the external telephone current calculated by the external telephone current calculation unit 239 to determine the arrival of excessive current from the line 104, and controls the relay 124 according to the determination result. Department. For example, the host unit 260 determines that an excessive current has arrived from the line 104 when the external telephone current is equal to or greater than a predetermined threshold.
The host unit 260 includes an external telephone hookup determination unit 161 , a line overcurrent determination unit 262 and a relay control unit 163 .
The external telephone hookup determination unit 161 and the relay control unit 163 of the host unit 260 in the second embodiment are the same as the external telephone hookup determination unit 161 and the relay control unit 163 of the host unit 160 in the first embodiment. .

The line overcurrent determining unit 262 determines that an overcurrent has arrived from the line 104 when the external telephone current calculated by the external telephone current calculating unit 239 exceeds a predetermined threshold value (for example, 150 mA). to decide.

The operation of determining an excessive current in the second embodiment will be described below.
In the following description, each current is defined by the following equations (1) to (4) as shown in FIG.
Line current = IA (1)
Silicon DAA current, which is the line current flowing in the silicon DAA 150 = IB (2)
External telephone current = IC (3)
Line current IA = silicon DAA current IB + external telephone current IC (4)

11 to 16 show the case where the mode of the communication terminal device 210 is fax standby (automatic reception mode), telephone standby (TEL mode) or DRD (Distinctive Ring Detection) mode, and the external telephone 103 is off-hooked from on-hook. 2 is a schematic circuit diagram showing an operation example of the .
As shown in FIG. 11, with the external telephone 103 on-hook, the relay 124 turned off, and the line 104 and the external telephone 103 connected, the line voltage of the silicon DAA 150 is The detector 153 detects the voltage V1 on the exchange 101 side. As a result, the line voltage acquisition unit 234 of the communication control unit 230 acquires the voltage V1 on the exchange 101 side. Here, the silicon DAA 150 side has not captured line 104 . The voltage V1 is also called a first voltage.

Next, the user hooks up the external telephone 103, as shown in FIG. In this case, current from line 104 flows to external telephone 103 via relay 124 .

In this case, as shown in FIG. 13, the line current IA flows through the photocoupler functioning as the external telephone hookup detector 127, and the external telephone hookup determination unit 161 detects that the external telephone 103 is off-hook. judged to have been The line 104 is also captured on the silicon DAA 150 side.

Next, as shown in FIG. 14, when the external telephone hookup determination unit 161 determines that the external telephone 103 has been off-hooked, the relay control unit 163 operates the relay drive circuit 125. , the relay 124 is turned on to disconnect the external telephone 103 from the line 104 .
In this state, the line voltage obtaining section 234 obtains the line voltage, and the line current obtaining section 235 obtains the line current IA. A known method may be used to detect the line current in the silicon DAA 150 . The line voltage obtained here is also called a line resistance voltage, and the line current IA obtained here is also called a first current.
Here, the switch side resistance value calculation unit 238 calculates the switch side resistance value R using the voltage V1 acquired in the state shown in FIG. can be calculated. The calculation method here will be described later.

Next, as shown in FIG. 15, the relay control unit 163 stops the operation of the relay drive circuit 125 and turns off the relay 124 to connect the external telephone 103 to the line 104 .
In this state, the line voltage detection unit 153 of the silicon DAA 150 detects the line voltage V2, and the line voltage acquisition unit 234 of the communication control unit 230 acquires the line voltage V2. Also, the line current acquisition unit 235 of the communication control unit 230 acquires the current flowing through the silicon DAA as the line current IB. The line voltage V2 obtained here is also called a second voltage, and the line current IB obtained here is also called a second current.

Then, the external telephone current calculator 239 calculates the external telephone current IC as follows.
First, the following formula (5) holds.
V1-V2=IA×R (5)
where R is the resistance of line 104;
Therefore, formula (5) is transformed into formula (6) IA=(V1-V2)/R (6)

Here, the following formula (7) holds.
IA = IB + IC (7)
By transforming this, the following formula (8) is obtained.
IC=IA-IB (8)
As a result, the external telephone current IC, which is the current flowing through the external telephone 103, can be calculated.

Also, the external telephone current calculator 239 can obtain the resistance value RT of the external telephone 103 by the following equation (9).
RT=V2/IC (9)

As described above, the voltage V1 of the exchange 101, the exchange-side resistance value R, and the resistance value RT of the external telephone 103 are obtained, so that the external telephone current IC flowing through the external telephone 103 in the state shown in FIG. 12 is obtained.

As a result, line overcurrent determination unit 262 determines that an overcurrent has arrived from line 104 when external telephone current IC is equal to or greater than the threshold. Then, as shown in FIG. 16, the DC loop formation instruction unit 132 instructs the DC loop formation unit 122 to release the line 104 from the silicon DAA 150, and the relay control unit 163 drives the relay. Activating circuit 125 turns on relay 124 and disconnects line 104 .
By performing such an operation, the photocoupler functioning as the external telephone hookup detector 127, the relay 124, and the external telephone 103 can be protected from excessive current coming from the line 104. FIG.

The relationship between the voltage V1 of the exchange 101, the line voltage V2, the exchange-side resistance value R, the line current IA, the silicon DAA current IB, the external telephone current IC, and the resistance value RT of the external telephone 103 as described above is shown in FIG. shown.

18 to 20 are schematic diagrams for explaining a method of calculating the resistance value R of the exchange 101. FIG.
As shown in FIG. 18, the voltage V1 on the exchange 101 side, the exchange side resistance value R, the resistance R _DAA when the silicon DAA 150 maintains DC, the voltage V _DAA when the silicon DAA 150 maintains DC, and , the line current I _DAA .

As shown in FIG. 19, when the external telephone 103 is on-hooked, the line current I _DAA =0A.
At this time, the voltage V _DAA becomes V _DAA =V1. This voltage can be detected by the line voltage detection unit 153 of the silicon DAA 150 and acquired by the line voltage acquisition unit 234 of the communication control unit 230 .

As shown in FIG. 20, line current _IDAA flows when external telephone 103 is off-hooked. This line current I _DAA can be acquired by the line current acquisition unit 235 of the communication control unit 230 via the silicon DAA 150, and the voltage V _DAA is also detected by the line voltage detection unit 153 of the silicon DAA 150 and used for communication. It can be obtained by the line voltage obtaining unit 234 of the control unit 230 .

Then, as shown in FIG. 20, the following formula (10) is obtained.
V1−V _DAA =I _DAA ×R (10)
The switch-side resistance value R is given by the following equation (11).
R=(V1−V _DAA )÷I _DAA (11)
As described above, the exchange-side resistance value calculator 238 of the communication control unit 230 can calculate the exchange-side resistance value R. FIG.

21 to 26 are schematic circuits showing operation examples when the mode of the communication terminal device 210 is telephone or fax standby (automatic switching mode between telephone and fax) and the external telephone 103 is switched from on-hook to off-hook. It is a diagram.
As shown in FIG. 21, with the external telephone 103 on-hook, the relay 124 turned off, and the line 104 and the external telephone 103 connected, the line voltage of the silicon DAA 150 is The detector 153 detects the voltage V1 on the exchange 101 side. As a result, the line voltage acquisition unit 234 of the communication control unit 230 acquires the voltage V1 on the exchange 101 side. The voltage V1 obtained here is also called a first voltage.
In this state, a ring signal arrives from the exchange 101 on the line 104 .

In such a case, as shown in FIG. 22, the silicon DAA 150 supplements line 104 to sense the voltage and current on line 104 . Then, the line voltage obtaining section 234 obtains the detected voltage as the line voltage, and the line current obtaining section 235 obtains the detected current as the line current IA. The line voltage obtained here is also called a line resistance voltage, and the line current IA obtained here is also called a first current.

Then, as shown in FIG. 23, communication terminal device 210 sounds a speaker (not shown) to prompt the user to hook up external telephone 103 .
Also, the pseudo RBT generator 136 of the communication control unit 230 generates a pseudo RBT and transmits it to the other party on the line 104 via the modem 140 and the silicon DAA 150 to notify the other party that it is being called.
Here, when the other party desires facsimile communication, a CNG (Calling) signal arrives from line 104 .

Next, the user hooks up the external telephone 103, as shown in FIG. In this case, current from line 104 flows to external telephone 103 via relay 124 .
In this state, the line voltage detection unit 153 of the silicon DAA 150 detects the line voltage V2, and the line voltage acquisition unit 234 of the communication control unit 230 acquires the line voltage V2. Also, the line current acquisition unit 235 of the communication control unit 230 acquires the current flowing through the silicon DAA as the line current IB. The line voltage V2 obtained here is also called a second voltage, and the line current IB obtained here is also called a second current.

Then, as shown in FIG. 25, the line 104 supplemented on the silicon DAA 150 side is released.
Here, the resistance value R on the exchange 101 side can be calculated from the voltage V1 of the exchange 101 obtained in FIG. 21 and the voltage and current of the line 104 detected in FIG.

Then, the external telephone current calculator 239 calculates the external telephone current IC and the resistance value RT of the external telephone 103 as described above.

As a result, line overcurrent determination unit 262 determines that an overcurrent has arrived from line 104 when external telephone current IC is equal to or greater than the threshold. Then, as shown in FIG. 26, the DC loop formation instruction unit 132 instructs the DC loop formation unit 122 to release the line 104 from the silicon DAA 150, and the relay control unit 163 drives the relay. Activating circuit 125 turns on relay 124 and disconnects line 104 .
By performing such an operation, the photocoupler functioning as the external telephone hookup detector 127, the relay 124, and the external telephone 103 can be protected from excessive current coming from the line 104. FIG.

27 to 32 are schematic circuit diagrams showing an operation example when the mode of the communication terminal device 210 is answering or fax standby (TAD mode) and the external telephone 103 is hooked from on-hook to off-hook.
As shown in FIG. 27, with the external telephone 103 on-hook, the relay 124 turned off, and the line 104 and the external telephone 103 connected, the line voltage of the silicon DAA 150 is The detector 153 detects the voltage V1 on the exchange 101 side. As a result, the line voltage acquisition unit 234 of the communication control unit 230 acquires the voltage V1 on the exchange 101 side. The voltage V1 obtained here is also called a first voltage.
In this state, a ring signal arrives from the exchange 101 on the line 104 .

In such a case, since the external telephone 103 has an answering machine function, the external telephone 103 responds to the ring signal from the line 104 and supplements the line 104 as shown in FIG. Furthermore, as shown in FIG. 29, the line 104 is also supplemented on the silicon DAA 150 side.

Next, as shown in FIG. 30 , relay control unit 163 operates relay drive circuit 125 to turn on relay 124 , thereby disconnecting external telephone 103 from line 104 .
In this state, the line voltage obtaining section 234 obtains the line voltage, and the line current obtaining section 235 obtains the line current. The line voltage obtained here is also called a line resistance voltage, and the line current IA obtained here is also called a first current.
27 and the line voltage and line current obtained in the state shown in FIG. A resistance value R can be calculated.

Further, as shown in FIG. 31, relay control unit 163 connects external telephone 103 to line 104 by operating relay driving circuit 125 and turning off relay 124 .
In this state, the line voltage acquisition unit 234 acquires the line voltage V2, and the line current acquisition unit 235 acquires the line current IB flowing through the silicon DAA 150. FIG. The line voltage V2 obtained here is also called a second voltage, and the line current IB obtained here is also called a second current.

Then, the external telephone current calculator 239 calculates the external telephone current IC and the resistance value RT of the external telephone 103 as described above.

As a result, line overcurrent determination unit 262 determines that an overcurrent has arrived from line 104 when external telephone current IC is equal to or greater than the threshold. Then, as shown in FIG. 32, the DC loop formation instructing unit 132 instructs the DC loop forming unit 122 to release the capture of the line 104 by the silicon DAA 150, and the relay control unit 163 drives the relay. Activating circuit 125 turns on relay 124 and disconnects line 104 .
By performing such an operation, the photocoupler functioning as the external telephone hookup detector 127, the relay 124, and the external telephone 103 can be protected from excessive current coming from the line 104. FIG.

Here, modes of the communication terminal device 110 described above will be described.
Fax standby (automatic reception mode) is a mode in which a ring signal from line 104 is detected and the mode automatically shifts to FAX reception.
Telephone or FAX standby (TEL or FAX automatic switching mode) is a mode in which the external telephone 103 is attached to the communication terminal device 110 and automatically determines whether the transmitter side is for FAX purposes or for telephone purposes.
Answering or fax waiting (TAD mode) is a mode in which the external telephone 103 having an answering machine function is attached to the communication terminal device 110, and the answering machine function communicates with the transmitter side.
The telephone standby (TEL mode) is a mode in which the external telephone 103 is attached to the communication terminal device 110 and the external telephone 103 is used as a telephone without detecting a ring signal from the line 104 .
The DRD mode is a mode in which a ring signal from the line 104 is turned on or off to shift to FAX reception or use the external telephone 103 as a telephone.

Part or all of the communication control units 130 and 230 and the host units 160 and 260 described above are stored in the memory 10 and the memory 10 as shown in FIG. It can be configured with a processor 11 such as a CPU (Central Processing Unit) that executes a program. Such a program may be provided through a network, or recorded on a recording medium and provided. That is, such programs may be provided as program products, for example.

Further, part or all of the communication control units 130 and 230 and the host units 160 and 260 are, for example, as shown in FIG. , a processing circuit 12 such as a parallel processor, ASIC (Application Specific Integrated Circuit), or FPGA (Field Programmable Gate Array).
As described above, the communication control units 130 and 230 and the host units 160 and 260 can be realized by processing circuitry.

In the first or second embodiment described above, the communication terminal devices 110 and 210 are, for example, MFPs or facsimiles. good.

110,210 communication terminal device, 111 line terminal, 112 telephone terminal, 113 scanner unit, 114 printing unit, 120,220 line control unit, 121 insulation transfer unit, 122 DC loop forming unit, 123 diode bridge, 124 relay, 125 relay Drive circuit 126 Excess current detector 127 External telephone hookup detector 130,230 Communication controller 131 Ring detection determination unit 132 DC loop formation instruction unit 133 DC loop formation determination unit 134,234 Line voltage Acquisition unit 135, 235 Line current acquisition unit 136 Pseudo RBT generation unit 137 FAX communication processing unit 238 Exchange side resistance value calculation unit 239 External telephone current calculation unit 140 Modem 150 Silicon DAA 160 Host unit 161 external telephone hookup determination unit, 162, 262 line overcurrent determination unit, 163 relay control unit.

Claims (5)

a line terminal connected to a line for communication;
a telephone terminal connected to an external telephone;
a switching unit connected between the line terminal and the telephone terminal for switching connection and disconnection between the external telephone and the line;
A communication terminal device, comprising: a control section that disconnects the line from the external telephone in the switching section when an excessive current arrives from the line. further comprising an excessive current detection unit disposed between the line terminal and the switching unit for detecting whether or not the current from the line is equal to or greater than a predetermined threshold;
The control unit causes the switching unit to switch between the external telephone and the line based on the detection result of the excessive current detection unit when the current from the line is equal to or greater than the predetermined threshold value. 2. The communication terminal device according to claim 1, wherein the communication terminal device is disconnected. 3. The communication terminal device according to claim 2, wherein the overcurrent detector is a photocoupler. 4. The communication terminal device according to claim 3, further comprising a resistor connected in parallel with the light emitting side of said photocoupler. The switching unit is arranged between the telephone terminal and the switching unit, and detects a non-conducting state of the external telephone when the current from the line does not flow through the external telephone, and switches the external telephone to the external telephone. an external telephone continuity detection unit for detecting a continuity state of the external telephone when a current is flowing from a line;
a DC loop forming unit that forms and cancels a DC loop with the line;
The external telephone continuity detecting section detects the non-conducting state, the switching section connects the external telephone and the line, and the DC loop forming section cancels the DC loop. acquires a first voltage that is the voltage of the line, the switching unit disconnects the external telephone and the line, and the DC loop forming unit forms the DC loop the line resistance voltage, which is the voltage of the line, is obtained, the external telephone continuity detection unit detects the continuity state, and the switching unit detects the connection between the external telephone and the line. a line voltage acquisition unit that acquires a second voltage that is the voltage of the line when the DC loop formation unit forms the DC loop;
When the switching unit disconnects the external telephone and the line and the DC loop forming unit forms the DC loop, a first current from the line is generated. the external telephone continuity detection unit detects the continuity state, the switching unit connects between the external telephone and the line, and the DC loop formation unit detects the DC loop a line current acquisition unit that acquires a second current that is a current from the line when forming
an exchange-side resistance value calculation unit that calculates an exchange-side resistance value, which is a resistance value on the exchange side included in the line, from the first voltage, the line resistance voltage, and the first current;
According to the first voltage, the second voltage, the line resistance voltage, the first current, the second current, and the exchange-side resistance value, the external telephone is turned on. and when the switching unit connects between the external telephone and the line and the DC loop forming unit forms the DC loop, the line is connected to the external telephone an external telephone current calculation unit for calculating an external telephone current that is the flowing current,
2. The communication terminal apparatus according to claim 1, wherein said control unit determines that said excessive current has arrived when said external telephone current is equal to or greater than a predetermined threshold.

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