JP3952051B2 - Communication terminal and program - Google Patents

Description

  The present invention relates to a communication terminal and a program suitable for use in an ISDN terminal incorporating a DSU.

  In an ISDN terminal with a built-in DSU, the user can generally switch between using a built-in DSU or disconnecting it and using an external DSU with a switch or the like. Further, the ISDN terminal disclosed in Patent Document 1 discloses a technique for automatically switching between built-in DSU and external DSU. The ISDN terminal is provided with a power supply monitoring unit that monitors the power supply state at the U point and S / T point of the built-in DSU. Then, it is determined whether or not the built-in DSU is operating based on the output signal of the power supply monitoring unit, and whether to use or disconnect the built-in DSU is automatically set based on the determination result.

  Patent Document 2 discloses a technique of providing a combined connector using a U-point connector and an S / T point connector in combination with an ISDN terminal. The ISDN terminal disclosed in Patent Document 2 is provided with a DSU synchronization signal detection circuit that detects whether or not a predetermined synchronization signal is included in the signal input from the combined connector. Note that this synchronization signal is a synchronization signal that the external DSU sends to the S / T point if an external DSU is connected. If the synchronization signal is detected, the built-in DSU is disconnected, and if the synchronization signal is not detected, the connection state of the switch provided therein is switched.

JP 2001-217955 A Japanese Patent Laid-Open No. 11-196154

By the way, the function of automatically switching whether or not to use the built-in DSU is not an essential function for ISDN terminals, but only one of “a function that is more convenient to be realized”. However, in each of the above-described techniques, in order to realize such automatic switching, hardware that is completely unnecessary is added if automatic switching is not performed. That is, in Patent Document 1, the power supply monitoring unit and the like, and in Patent Document 2, the DSU synchronization signal detection circuit are the added hardware. As described above, each of the above techniques has a problem in that additional hardware is required to realize automatic switching, resulting in an increase in cost.
The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a communication terminal and a program capable of realizing automatic switching of a network termination device while suppressing an increase in cost.

In order to solve the above problems, the present invention is characterized by having the following configuration. The parentheses are examples.
In the configuration of the first aspect, connectable intermediate interface point external network termination device (34) and (S / T point), it may be connected to the communication network and said intermediate interface point (S / T point) A built-in network termination device (14), a terminal unit (102) connected to the intermediate interface point (S / T point), the built-in network termination device (14), and the intermediate interface point (S / T point); In the communication terminal having the switching means (12) for setting the on / off state of the connection between the terminal unit (102), the terminal unit (102) is connected to the terminal unit (102 via the intermediate interface point (S / T point). ) and said external network termination device (34) or the internal network units (determination process of determining whether it is possible to communicate with either a network terminating device of 14) (SP10), the determination result in said determination step That it was negative Wherein the has a switching means switching process for switching the ON / OFF state of (12) (SP 12) and repeating while at the prescribed waiting time execution control means (2, 4) the condition.
Further, in the configuration according to claim 2, in the configuration according to claim 1, the control means (2, 4) has a predetermined control signal (INFO1) for the intermediate interface point (S / T point). , INFO3 signal), and based on whether a response signal (INFO2, INFO4 signal) corresponding to the control signal is returned, it is determined whether communication with any one of the network termination devices is possible. Features.
Further, in the configuration of claim 3, wherein, the intermediate interface point can be connected to an external network termination device (34) and (S / T point), connected to the communication network and said intermediate interface point (S / T point) A built-in network termination device (14), a control unit (2) and a terminal unit (102) connected to the intermediate interface point (S / T point), the built-in network termination device (14), A program executed in the control device (2) of a communication terminal having switching means (12) for setting an on / off state of a connection with an intermediate interface point (S / T point), Whether the terminal unit (102) can communicate with any one of the external network termination device (34) and the built-in network termination device (14) via the intermediate interface point (S / T point) Overjudgment And (SP10), on condition that the determination result of the determination process (SP10) is negative, the switching means (12) on / switching process (SP 12) for switching the off-state and a predetermined waiting time It is characterized by being repeatedly executed while being separated.
Furthermore, in the configuration according to claim 4, in the configuration according to claim 3, the terminal unit (102) sends a predetermined control signal (INFO 1, INFO 3) to the intermediate interface point (S / T point). Signal) and a response signal (INFO2, INFO4 signal) corresponding to the control signal is received, and the determination process determines whether the response signal (INFO2, INFO4 signal) is normally received. And determining whether communication with any one of the network termination devices is possible.

The function of determining whether or not communication is possible via the intermediate interface point (S / T point) in the control means is a function that the terminal unit should have even if automatic switching is not performed, and the determination result is negative. As long as this state continues, the function of repeatedly switching the on / off state of the switching means can be realized by software without adding new hardware. Thereby, according to this invention, the automatic switching function is realizable, suppressing the cost increase by addition of new hardware.

1． Hardware Configuration of Embodiment Next, the configuration of an ISDN terminal of an embodiment of the present invention will be described with reference to FIG.
In FIG. 1, reference numeral 100 denotes the ISDN terminal of this embodiment, and the built-in DSU 14 provided in the terminal is connected to the ISDN network 40 via the U point terminal 16. Reference numeral 18 denotes an S / T point terminal which inputs and outputs signals of the S point and T point protocols. The S / T point terminal 18 and the range of connection connected thereto are S / T points. A switch 12 sets an on / off state of a connection between the S / T point side terminal of the built-in DSU 14 and the S / T point.

  A CPU 2 controls each unit in the ISDN terminal 100 via the bus 7 based on a control program stored in the flash memory 4. For example, the on / off state of the switch 12 is controlled by the CPU 2. A RAM 6 is used as a work memory for the CPU 2. Reference numeral 8 denotes a LAN interface, which inputs and outputs IP packets with a personal computer or the like. Reference numeral 10 denotes an S / T point interface, which inputs and outputs S point and T point protocol signals to and from the S / T point. The terminal adapter part 102 is comprised by the above components 1-10. The S / T point terminal 18 is connected to an ISDN device such as a facsimile machine 30 and a telephone 32 or an external DSU 34 as necessary. The external DSU 34 can be connected to the ISDN network 40 in the same manner as the built-in DSU 14, but in a normal usage method, only one of the external DSU 34 or the built-in DSU 14 is connected to the ISDN network 40.

2． Next, the operation of this embodiment will be described. First, when the terminal adapter unit 102 is activated, an operation for establishing a physical layer (layer 1) with any DSU connected to the S / T point is executed in the following sequence. First, the INFO1 signal (activation request signal) is output from the terminal adapter unit 102 to the S / T point. When this INFO1 signal is received by any DSU, the INFO2 signal is returned from the DSU to the terminal adapter unit 102. By this INFO2 signal, the terminal adapter unit 102 can synchronize with the DSU, and the INFO3 signal having a normal frame configuration is returned from the terminal adapter unit 102 to the DSU. Next, an INFO4 signal having a normal frame configuration is returned from the DSU to the terminal adapter unit 102.

  When the above operation is normally completed, a physical layer is established between the corresponding DSU and the terminal adapter unit 102. Thereafter, the INFO3 signal is periodically sent from the terminal adapter unit 102, and the DSU returns the INFO4 signal in response to this, whereby the state where the physical layer (layer 1) is established is maintained. Each of the above signals is stipulated in “CCITT standard I.430”. These signals are used not only in the terminal adapter unit 102 but also in other terminals (facsimile device 30, telephone 32, etc.) communicating with the DSU. It is an essential function to send and receive.

  In the present embodiment, when the terminal adapter unit 102 is activated, the DSU connection routine shown in FIG. In the figure, when the process proceeds to step SP10, it is determined whether or not a physical layer is established at the S / T point. If "NO" is determined here, the process proceeds to step SP12, and the on / off state of the switch 12 is changed. That is, if it is currently on, it is changed to an off state, and if it is currently off, it is changed to an on state. On the other hand, if “YES” is determined in step SP10, step SP12 is skipped, and the state of the switch 12 is maintained as it is. Next, when the process proceeds to step SP14, the process waits for a predetermined time (about several seconds), and then the process returns to step SP10. Thereafter, the processing of steps SP10 to SP14 is repeatedly executed. Next, a specific operation according to the state of each DSU will be described based on the above operation.

(1) When both DSUs cannot communicate When both the built-in DSU 14 and the external DSU 34 are not connected to the ISDN network 40, INFO1, INFO3 output from the terminal adapter unit 102 regardless of the state of the switch 12. There is no DSU that returns the INFO2 and INFO4 signals in response to the signal. Therefore, the terminal adapter unit 102 cannot establish a physical layer. Thereby, it is always determined as “NO” in step SP10, and the on / off state of the switch 12 is switched at every predetermined time.

(2) Case where only built-in DSU 14 can communicate Next, it is assumed that only built-in DSU 14 is connected to ISDN network 40 and external DSU 34 is not connected. If the switch 12 is off, the INFO1 and INFO3 signals output from the terminal adapter unit 102 do not reach the built-in DSU 14 and reach only the external DSU 34, but the external DSU 34 is not in a communicable state. Eventually, none of the DSUs returns INFO 2 and INFO 4 signals to the terminal adapter unit 102. Therefore, when step SP10 is executed next, it is determined “NO”, and in step SP12, the switch 12 is changed to the on state. When the switch 12 is turned on, a physical layer is established between the terminal adapter unit 102 and the built-in DSU 14, and thereafter, “YES” is always determined in step SP10. Thereby, the switch 12 is maintained in the ON state.

(3) When only the external DSU 34 can communicate Next, it is assumed that only the external DSU 34 is connected to the ISDN network 40 and the built-in DSU 14 is not connected. Since the terminal adapter unit 102 and the external DSU 34 are connected via the S / T point terminal 18, the external DSU 34 returns the INFO2 and INFO4 signals in response to the INFO1 and INFO3 signals output from the terminal adapter unit 102. If the switch 12 is in the ON state, the INFO1 and INFO3 signals reach the built-in DSU 14, but the built-in DSU 14 is not connected to the ISDN network 40, so no signal is returned. Therefore, when only the external DSU 34 can communicate, a physical layer is established between the terminal adapter unit 102 and the external DSU 34 regardless of the on / off state of the switch 12, and therefore the on / off state of the switch 12 is undetermined. Thus, the state where the switching does not occur is continued.

(4) When both DSUs can communicate Next, a case is assumed where both the built-in DSU 14 and the external DSU 34 are connected to the ISDN network 40. If the switch 12 is on, the INFO1 and INFO3 signals output from the terminal adapter unit 102 reach both the built-in DSU 14 and the external DSU 34. Since both DSUs try to return INFO2 and INFO4 signals, these signals collide on the S / T point, and the terminal adapter unit 102 cannot establish a physical layer for any DSU. . In such a case, “NO” is determined in step SP10, and the switch 12 is changed to an off state in step SP12. When the switch 12 is changed to the OFF state, only the external DSU 34 returns the INFO 2 and INFO 4 signals in response to the INFO 1 and INFO 3 signals, so that a physical layer is established between the terminal adapter unit 102 and the external DSU 34. Is kept off.

  As described above, according to the present embodiment, based on whether or not the physical layer (layer 1) is established in the terminal adapter unit 102 which is one of the terminals connected to the S / T point, the switch 12 When at least one of the built-in DSU 14 and the external DSU 34 is communicable with the ISDN network 40, the communicable DSU and each terminal (terminal adapter unit 102, facsimile apparatus 30, telephone device) 32 etc.) can be ensured. The function of determining whether or not the physical layer (layer 1) is established is an essential function for these terminals regardless of whether or not the DSU is automatically switched. Therefore, in this embodiment, there is no newly added hardware for performing automatic switching of DSU, and it can be understood that automatic switching of DSU can be realized at a very low cost.

3． Modifications The present invention is not limited to the above-described embodiments, and various modifications can be made as follows, for example.
(1) In the above embodiment, an example in which the present invention is applied to an ISDN terminal has been described. However, the present invention is not limited to an ISDN terminal, and a plurality of communication networks and intermediate interface points (for example, S / T points) are used. The present invention can be applied to any communication terminal that can connect a network termination device (for example, DSU) and adopts a protocol that selects and uses one of these network termination devices.
(2) In the above embodiment, the DSU switching process is executed by a program (DSU connection routine) operating on the CPU 2, but only the program is stored in a recording medium such as a CD-ROM or a flexible disk and distributed. Alternatively, it can be distributed through a transmission line.

It is a block diagram of the ISDN terminal of one Example of this invention. It is a flowchart of a DSU connection routine.

Explanation of symbols

  2: CPU (control device), 4: Flash memory, 6: RAM, 7: Bus, 8: LAN interface, 10: S / T point interface, 12: Switch, 14: Built-in DSU, 16: U point terminal, 18 : S / T point terminal, 30: facsimile machine, 32: telephone, 34: external DSU, 40: ISDN network, 100: ISDN terminal, 102: terminal adapter unit (terminal unit).

Claims (4)

Wherein the external network unit intermediate interface point connectable, the internal network unit which may be connected to the communication network and said intermediate interface point, a terminal portion connected to the intermediate interface point, and the internal network unit intermediate In a communication terminal having switching means for setting an on / off state of a connection with an interface point,
The terminal unit includes: a determination step of determining whether it is possible to communicate with either a network terminating device of the terminal portion is the external network unit or the built network unit via the intermediate interface point, the determination A communication terminal comprising: a control unit that repeatedly executes a switching process of switching the on / off state of the switching unit with a predetermined waiting time on condition that a determination result in the process is negative .   The control means transmits a predetermined control signal to the intermediate interface point, and based on whether or not a response signal corresponding to the control signal is returned, whether or not communication with any one of the network termination devices is possible The communication terminal according to claim 1, wherein the communication terminal is determined. And the external network unit intermediate interface point connectable, the internal network unit which may be connected to the communication network and said intermediate interface point, a terminal portion connected to the intermediate interface point and having a control device, the built network A program executed in the control device of a communication terminal having switching means for setting an on / off state of a connection between a termination device and the intermediate interface point,
A determination process for determining whether the terminal unit can communicate with either the external network termination device or the built-in network termination device via the intermediate interface point;
A program characterized by repeatedly executing a switching process for switching the on / off state of the switching means with a predetermined waiting time on condition that the determination result of the determination process is negative. The terminal unit transmits a predetermined control signal to the intermediate interface point, and receives a response signal corresponding to the control signal;
The program according to claim 3, wherein the determination step is a step of determining whether or not communication with any one of the network termination devices is possible based on whether or not the response signal is normally received.

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