JPH08335987A - Modem and its mode changeover method - Google Patents

Abstract

PURPOSE: To make a general user unable to set a transmission level or the like by providing a mode utilized only an engineer specifically qualified. CONSTITUTION: When a 2nd escape command is given from a computer system 1 to a MODEM 2, the MODEM 2 is set from the on-line mode to the 2nd escape mode and accepts a 2nd escape 2nd command setting command. The MODEM 2 sets the 2nd escape 2nd command according to the 2nd escape 2nd command setting command. When the 2nd escape 2nd command is inputted again in a prescribed time after the 2nd escape 2nd command is inputted by the computer system 1, a command for setting a transmission level or the like inputted by a specifically qualified engineer only is accepted and executed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a modulator / demodulator (mod) used by being connected between a computer system and a telephone network or the like.
MODULATOR-DEMODULATOR (so-called MODEM) and its mode switching method.

[0002]

2. Description of the Related Art A modulator / demodulator is used when one computer system and another computer system are connected via a telephone network and data communication is performed between these computer systems. The modulator / demodulator is connected between a computer system or a network system and a telephone line network, modulates a digital signal representing data handled by these systems into an analog signal which can be transmitted by the telephone line, and vice versa. The signal is demodulated into a digital signal.

The conventional modulator / demodulator has a command mode, an online mode, and an escape mode. In the command mode, the command related to the start of communication given from the computer system is executed with the line disconnected, and the communication parameters such as communication speed are set or changed, off-hook, and dialing is performed. Mode. The online mode modulates a digital signal representing data to be transmitted, which is supplied from the computer system, into an analog signal and sends the analog signal to the telephone line network.
In addition, it is a mode in which an analog signal from the telephone network is demodulated into a digital signal and output to the computer system. Escape mode is used when you want to change communication parameters such as communication speed while you are performing data communication in online mode. In the escape mode, the command given from the computer system is executed while the line is connected.

The modulator / demodulator enters the command mode when the power is turned on or reset by the user. In this command mode, when a command relating to the setting of communication parameters is input to the computer system by the user and given to the modulator / demodulator, the process according to the command is executed by the modulator / demodulator to set or change the communication parameters. It In this command mode, the user enters commands into the computer system to connect to that computer system for data communication with the other computer system. When this command is given to the modem, the modem executes the command (dialing). Then, a telephone line is connected between the modulator / demodulator and the modulator / demodulator connected to the other computer system. When the telephone line is connected, both of the two modulation / demodulation devices shift to the online mode, and data communication is performed between the two computer systems via the two modulation / demodulation devices and the telephone line network.

When the user wants to change communication parameters while data communication is being performed, the user gives a mode switching command for switching to the escape mode from the computer system to the modem in the online mode. This causes the modulator / demodulator to transition from the online mode to the escape mode. That is, the modulation / demodulation device can receive a command from the computer system for stopping the data communication and changing the communication parameter etc. while maintaining the connection of the telephone line with the other modulation / demodulation device. . After changing the communication parameters etc., the modulator / demodulator returns to the online mode again and the data communication is continued.

When ending the data communication, the user shifts the modulator / demodulator from the online mode to the escape mode. In this escape mode, a command to disconnect the telephone line is entered by the user into the computer system. When this command is given to the modem, the modem executes the command and disconnects the telephone line. When the telephone line is disconnected, 2
The modems enter the command mode.

On the other hand, the Telecommunications Business Law stipulates that the transmission level (voltage) of the analog signal transmitted from the modulator / demodulator should be adjusted so that the reception level at the telephone station becomes -15 [dB] or higher. There is. If the telephone line from the modulator / demodulator to the telephone station becomes long, the analog signal transmitted from the modulator / demodulator may be attenuated, and the reception level at the telephone station may become lower than the specified value. In such a case, it is necessary to change the transmission level of the analog signal from the modulator / demodulator so that the reception level of the analog signal at the telephone station becomes a specified value. This transmission level change is
This is done by inputting a transmission level change command for changing the transmission level in the escape mode from the computer system to the modem. The transmission level can be changed only by a technician who is qualified to make settings based on the Telecommunications Business Act, and cannot be performed by general users who do not have this qualification. Therefore, this transmission level change command can be known only to qualified engineers.

However, a general user who is not qualified is
The transmission level change command may be found by trial and error. Then, a general user who is not allowed to change the transmission level may change the transmission level freely.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a modulator / demodulator with a new mode for executing a specific command that can be input only by an engineer having a specific qualification, and only the engineer can change the transmission level in the new mode. The purpose is to be able to do.

The modulator / demodulator is used by being connected between a computer system and a telephone network. This modulator / demodulator has a command mode for executing a first type of command including a command for starting communication, which is input from a computer system in a state where the line is disconnected, and a state where the line is connected, An online mode in which a signal input from a computer system is modulated and transmitted to a telephone line network and a signal input from the telephone line network is demodulated and given to the computer system, and a computer connected to the line is connected. Second command that is input from the system or that contains commands related to changing communication parameters
Has a first escape mode for executing the following types of commands.

The modulator / demodulator according to the present invention executes the second escape mode (process) for executing the third type of command including the command relating to the change of the communication parameter, which is inputted from the computer system in the state where the line is connected. Means) is newly provided.

The mode switching method according to the present invention is a method for shifting the modulator / demodulator to the second escape mode. When the online mode is set, the mode switching method inputs the first signal and the first signal. When a second escape command including a second signal of a predetermined length continuous at least immediately before or after the first signal is received, the second escape mode is entered, and in this second escape mode It accepts a third signal input from the computer system and a signal concerning its length and registers these signals, and then continues the first signal and at least one of immediately before or after the first signal. A state in which a command of the third type can be received, provided that a third signal having the registered length is received. A.

According to a third aspect of the present invention, there is provided a modulation / demodulation device which is input from a computer system in a state where a line is connected and which includes a command regarding a change of communication parameters.
Second escape mode processing means for executing commands of the type: and a first signal input from the computer system and at least one of immediately before or after the first signal when in the online mode. A mode switching means is provided for activating the second escape mode processing means when a second escape command including a continuous second signal of a predetermined length is received. The second escape mode processing means receives a third signal inputted from the computer system and a signal relating to the length thereof and registers these signals, and thereafter, the first signal and the first signal. The command of the third type can be accepted on condition that the third signal having the registered length continuous at least immediately before or immediately after is accepted.

First executed in command mode
The commands of type include a command indicating the start of communication such as on-hook and dialing, and a command for setting or changing communication parameters such as communication speed.

The second type of command executed in the first escape mode includes a command for changing communication parameters, a command for disconnecting a line, and the like. The second type of command may partially overlap (or be similar to) the first type of command.

The third type of command executed in the second escape mode includes a command for changing the transmission level of the signal transmitted from the modulator / demodulator. This command can be used only by a specific engineer. Other commands that are not recommended to be used by general users (for example, communication protocol change commands)
May be included in the third type command. The third type command may include a part of the second type command.

According to the present invention, the second escape mode is entered only when the second escape command which can be known only to a specific engineer is input. Since the general user who does not know the second escape command cannot shift to the second escape mode, the general user cannot change the transmission level which is prohibited by the general user.

Further, according to the present invention, in order to accept the command of the third type for changing the transmission level, etc., after shifting to the second escape mode,
It is necessary to input the third signal and a signal related to the length thereof, and then it is necessary to further input the first signal and the third signal having the input length. Since the general user does not know such a procedure, the general user cannot change the transmission level using the third type command even if the second escape mode is entered for some reason. .

Preferably, in the second escape mode, only when the password input from the computer system has a predetermined conflict with a predetermined password, the third signal and the signal relating to the length of the third signal are transmitted. Be prepared to accept it.

By doing so, only a specific engineer who knows the password can input the command of the third type, and it is possible to surely avoid the situation in which the general user inputs the command of the third type.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a configuration in which two computer systems are connected via a telephone network.

In some cases, the two computer systems are in a superordinate and subordinate relationship (for example, computer
In some cases, the system 4 is a host computer (or a server) and the computer system 1 is a terminal (or a client), and there is an equivalent relationship.
The computer system itself is a known system.

In order to perform data communication between the two computer systems 1 and 4 via the telephone network, a modem (mo) is used between the computer system 1 and the telephone network.
dmoderator-demodulator (MODEM) 2 is connected, and a modem 3 is connected between the computer system 4 and the telephone network. Generally, the modem is the RS of the computer system.
It is connected to the -232C port. The modem may also be connected to the network system. In this case, the modem is a computer included in the network system.
Connected to the system or to the network bus.

Communication software (communication program) is stored in the computer system 1. This communication software outputs data or commands input to the computer system 1 by a user or a technician to the modem 2 and data input to the computer system 1 from the modem 3 to the computer system 1.
It is stored in the internal memory, external storage device, etc., or is displayed on the display device. Computer system 4
Similar communication software is set up.

FIG. 2 is a block diagram showing the detailed structure of the modem. Since the modem 2 and the modem 3 have exactly the same configuration, only one modem 2 will be described. The modem 2 has an interface circuit 11, a CPU 12, a modulation / demodulation circuit 1
3, NCU (Network Control Unit) 14,
It is composed of a ROM 15 and a RAM 16.

The ROM 15 is a program for realizing processing such as reception and execution of commands described later, error correction during communication, data compression / expansion, input monitoring / judgment of first and second escape commands, and the like. Is stored in advance. The RAM 16 stores various preset commands (including the first escape command and the second escape command), and also stores commands or parameters such as communication speed given by the computer 1 or data. . A predetermined storage location in RAM 16 is also used as a timer. The CPU 12 operates according to a program previously stored in the ROM 15.

The voltage level of the input / output digital signal of the computer system 1 is different from the voltage level of the input / output digital signal of the CPU 12. The interface circuit 11 is for connecting the computer system 1 and the modem 2 by performing voltage conversion of these digital signals. The modulation / demodulation circuit 13 modulates the digital signal from the CPU 12 into an analog signal and supplies it to the NCU 14, and conversely demodulates the analog signal from the NCU 14 into a digital signal and supplies it to the CPU 12. The voltage level of the analog signal flowing through the telephone network and the voltage level of the input / output analog signal of the modulation / demodulation circuit 13 are different. N
The CU 14 converts the voltage of these analog signals to connect the modem 2 to the telephone network. These interface circuit 11, modulation / demodulation circuit 13 and N
CU14 is known.

FIG. 3 is a state transition diagram in the modem 2 (the same applies to the state transition diagram in the modem 3). FIG. 4 shows a computer system 1 originating a call, a modem 2,
3 shows a connection state in each mode when the data communication is performed by connecting to the computer system 4 through 3.

The modems 2 and 3 have a command mode, an online mode, a first escape mode and a second mode.
There is an escape mode. Of these, the command
The mode, online mode and first escape mode can be used by general users. The second escape mode cannot be used by general users, and can be used only by an engineer who is qualified to set (including change) communication conditions based on the Telecommunications Business Act.

The command mode is as shown in FIG.
This is a state in which the computer system 1 and the modem 2 are connected (a state in which data and commands can be sent and received between the computer system 1 and the modem 2). In this command mode, the modem 2 executes the command given from the computer system 1. command·
In the mode, commands given from the computer system 1 to the modem 2 include, for example, setting or changing communication parameters such as communication speed, dialing (line connection) to the other party.

In the command mode, the user or technician sends a character string representing a command through the keyboard of the computer system 1 to the computer system 1.
To enter. This string is for computer system 1
It is output from the RS-232C port and given to the modem 2. When the user or technician clicks the icon or button displayed on the display screen of the display device of the computer system 1 with the mouse, the command represented by the clicked icon or button is output from the RS-232C port of the computer system 1. It may be given to the modem 2. In this way, a user or a technician inputting a command to the computer system 1 and giving it to the modem 2 is hereinafter simply referred to as inputting a command.

The modem 2 receives a command given from the computer system 1, and if the command conforms to a preset format (for example, it corresponds to one of a plurality of predetermined commands). Execute the command, including the command, if there is a specified number or specified digits of parameters following the command). When the modem 2 executes the command, the result is returned to the computer system 1. The execution result of the command by the modem 2 is displayed on the display device of the computer system 1.

When the power of the modem 2 is turned on by the user or the technician, or when the modem 2 is reset by the user or the technician, the modem 2 enters the command mode. When the telephone line is disconnected by the user or the technician pressing the line disconnection button provided in the modem 2 for disconnecting the telephone line in the online mode, or the first escape
When a disconnection command for disconnecting the telephone line in the second mode and the second escape mode is given from the computer system 1, the modem 2 shifts from these modes to the command mode.

The online mode is a mode in which the two computer systems 1 and 4 are connected via the modems 2 and 3 and the telephone network, and the computer systems 1 and 4 perform data communication. .

In the online mode, the user or technician inputs data to be transmitted to the computer system 2 from the keyboard of the computer system 1. The computer system 1 outputs the input data to the modem 2 from the RS-232C port under the control of the communication software. Data stored in advance in the internal memory of the computer system 1, data stored in an external storage device such as a hard disk, or data read from a recording medium such as a floppy disk is transferred to the modem 2 through the RS-232C of the computer system 1. May be given to. The modem 2 modulates the data given from the computer system 1 and sends it to the modem 3 via the telephone line network.

When data is received from the modem 3 via the telephone network, the modem 2 demodulates the received data and transfers it to the computer system 1. The computer system 1 writes the data on a magnetic recording medium which stores the data in an internal memory or a storage device of the computer system 1. Or, if necessary, display on the display device.

In the command mode, when a line connection command for connecting the computer system 1 to the computer system 4 is given from the computer system 1 to the modem 2, the modem 2 executes this command. That is, the modem 2 sends a dial signal to the telephone network. When the modems 2 and 3 are connected by the telephone network (the modem 2 and the computer system 1, and the modem 3 and the computer system 4 are already connected), these modems 2 and 3 are both online from the command mode.・ Move to the mode. Similarly, when dialing from modem 3 to modem 2,
And the modem 3 are connected by a telephone network, these modems 2 and 3 are brought online from the command mode.
Switch to mode. Further, when a return command for returning to the online mode in the first escape mode and the second escape mode is given from the computer system 1, the modem 2 returns from those modes to the online mode.

The first escape mode is a state in which the computer system 1 and the modem 2 are connected, and the modem 2 and the modem 3 are connected via the telephone network (the modem 3 is in the online mode). It is a mode in which the modem 2 executes a command given from the computer system 1 while maintaining the connection with the telephone line network. Examples of commands input from the computer system 1 include commands for setting or changing communication parameters such as communication speed, and commands for disconnecting the line to terminate communication. Input of commands from the computer system 1 and execution of commands in the modem 2 are performed in the same manner as in the command mode. When the modem 2 is in the first escape mode, the modem 3 remains in the online mode as described above, and the modem 3 and the computer system 4 are exchanging data. When data is transmitted from the computer system 4 via the modem 3 and the telephone network while the modem 2 is in the first escape mode, the data transmitted from the modem 2 modem 3 is ignored.

In the online mode, when the first escape command is given from the computer system 1, the modem 2 shifts to the first escape mode. This first escape command is a command consisting of a predetermined character string that is not included in communication data. For example, as shown in FIG. 5 (A), before and after the three character "+" codes (before or after Either one of the latter may be used), and there is a section in which there is no data (character code) for 1 second or more.

As described above, the modem 2 returns to the online mode when the return command is given from the computer system 1 in the first escape mode, and the line is turned off when the line disconnection command is given from the computer system 1. After disconnecting, return to command mode.

The second escape mode is a mode in which the modem 2 executes a command given from the computer system 1 while maintaining the connection with the telephone line network, like the first escape mode. In the second escape mode, the modem 2 executes a specific command in addition to the command input in the first escape mode. This specific command can only be performed by a technician who has the qualifications of communication parameters that can make settings (including changes) based on the Telecommunications Business Act, and cannot be performed by general users. For example, from the modem 2 to the telephone line. It includes a command for changing the transmission level of the analog signal transmitted to the network. A command for setting or changing a communication parameter of the modem 2 which is not preferable to be performed by a general user can be input only in the second escape mode. The specific command that can be input only in the second escape mode can be known only to the above-mentioned technician and is not notified to general users.

As described above, the modem 2 returns to the online mode when the return command is given from the computer system 1 in the second escape mode, and the line is disconnected when the line disconnection command is given from the computer system 1. After disconnecting, return to command mode. Further, as will be described later, if there is a setting failure or an input failure in the second escape mode, the modem 2 returns to the online mode.

The second escape mode includes a second escape second command setting process, a second escape second command input process, and a command input and execution process, and these processes are executed in this order. This completes the operation of the second escape mode. Details of these processes will be described below.

When the second escape command is given from the computer system 1 in the online mode, the modem 2 shifts to the second escape mode. This second escape command is a command that is different from the first escape command and that consists of a character string that may not be included in communication data, and as shown in FIG. A sequence of character codes in which a given code (eg, the character “−” code) continues before and after the code (either before or after it) for a given time (eg, 60 minutes).

In the second escape mode, first, the second escape second command is set. That is,
The second escape second command setting command is input by the technician from the computer system 1. If the input second escape second command setting command conforms to a predetermined format, the command is set to the modem 2
To run. As a result, the second escape second command is stored in the RAM 16. The second escape second command setting command is, for example, the following command.

AT: Z * 70

"AT: Z" indicates that the command is the second escape second command setting command,
“*” Represents a character that is consecutive (before or after) of the three-digit character “+” code in the second escape command, and “70” indicates that character code is “*”. It represents the time (minutes) to continue. The second escape second command set according to the second escape second command setting command is, as shown in FIG. 5C, before and after the three character "+" codes (either before or after). A character code "*" is a sequence of character codes that continues for 70 minutes.

Then, the engineer inputs the second escape second command set by the second escape second command setting command twice from the computer system 1 by the same command. Only when the second correct command is input within a predetermined time after the first correct command is input, the modem 2 shifts to command input and execution processing.

When a technician gives a command (character string) for setting or changing the transmission level, the protocol, etc., to the modem 2 if the command conforms to a preset format. The modem 2 executes the command (for example, including a command corresponding to one of a plurality of predetermined commands, a predetermined parameter exists following the command, etc.).

When the second escape second command setting command is not input from the computer system 1 or when the input second escape second command setting command does not conform to the format preset in the modem 2 ( (Setting failure), the modem 2 shifts to the online mode. If the entered one does not match the set second escape second command, or 2
When the second escape second command for the second time is not input within a predetermined time (input failure), the modem 2 is online.
Switch to mode. Since such a procedure (procedure) can be known only by the technician having the above-mentioned setting, it is almost impossible for the general user to proceed to the step of inputting the second escape second command. In this way, the general user cannot set or change the communication parameters that the general user cannot perform, and the general user cannot set or change the condition of the modem, which the general user does not like.

FIG. 6 shows the modem 2 in command mode.
The processing procedure of is shown.

The modem 2 enters the command mode when the power is turned on or reset by the user or the technician. Further, when the telephone line is disconnected by the user or the technician pressing the line disconnection button provided in the modem 2 in the online mode, or in the first escape mode and the second escape mode,
After the line disconnect command is given from the computer system 1 to disconnect the line, the modem 2 shifts from those modes to the command mode.

The modem 2 accepts a command input by the user or an engineer and given from the computer system 1 (step 21), and judges whether the command conforms to a predetermined format (step 22).
If it is determined that the command does not conform to the predetermined format (NO in step 22), the fact is notified to the computer system 1.

When the modem 2 determines that the command given from the computer system 1 to the modem 2 is other than the line connection command (NO in step 23), the modem 2 performs a process according to the command (step twenty four).
The processing result is from the modem 2 to the computer system 1.
The computer system 1 displays the processing result on the display device.

In step 23, when the modem 2 determines that the command given from the computer system 1 is a line connection command (YES in step 23), the modem 2 performs a process of connecting to the modem 3 via the telephone line network (step S23). Step 25). After this, the modem 2 shifts from the command mode to the online mode (step 26) and notifies the computer system 1 to that effect.

FIG. 7 is a flow chart showing the processing procedure of the modem 2 in the online mode.

When the modem 2 executes the line connection command in the command mode and connects to the modem 3 via the telephone line as described above, it shifts to the online mode.

When the telephone line is disconnected by pressing the line disconnection button of the modem 2 by the user or the technician (YES in step 31), the modem 2 shifts from the online mode to the command mode (step 35). Notify the computer system 1 to that effect.

When the first escape command is given from the computer system 1 to the modem 2 (step 32)
YES), the modem 2 shifts from the online mode to the first escape mode (step 36) and notifies the computer system 1 to that effect.

When the second escape command is given from the computer system 1 to the modem 2 (step 33)
YES), the modem 2 shifts from the online mode to the second escape mode (step 37) and notifies the computer system 1 to that effect.

In the online mode, the modem 2 mainly modulates the data supplied from the computer system 1 and transmits the data to the modem 3 via the telephone line, and the data supplied from the modem 3 via the telephone line. Demodulate and give to computer system (step 3)
Four).

FIG. 8 shows the processing procedure of the modem 2 in the first escape mode.

The modem 2 is connected to the online
In the mode, when the first escape command is given from the computer system 1, the first escape command
Switch to mode.

The modem 2 accepts a command input by the user or a technician and given from the computer system 1 (step 41), and determines whether the command conforms to a predetermined format (step 42).
If it is determined that the command does not conform to the predetermined format (NO in step 42), the fact is notified to the computer system 1.

If the modem 2 determines that the command given to the modem 2 from the computer system 1 is the return command (YES in step 43), the modem 2 shifts from the first escape mode to the online mode. Then (step 46), the computer system 1 is notified to that effect.

When the modem 2 determines that the command given to the modem 2 from the computer system 1 is the line disconnection command (YES in step 44), the modem 2 performs a process of disconnecting the telephone line (step 47), Switch from the first escape mode to the command mode (step
48), and to that effect is given to the computer system 1.

When the command given from the computer system 1 to the modem 2 is other than the return command and the line disconnection command, the modem 2 performs a process according to the command (step 45),
Return to system 1. The computer system 1 displays the processing result on the display device.

FIG. 9, FIG. 10 and FIG. 11 show the second escape
The processing procedure of the modem 2 in the mode is shown.

As described above, the modem 2 is online,
In the mode, when the second escape command is given from the computer system 1, the second escape command
Switch to mode.

The modem 2 accepts the command input by the technician and given from the computer system 1 (step 49), and judges that the command given from the computer system 1 is the line disconnection command (YES in step 50). ), The telephone line is disconnected (step 51), the second escape mode is changed to the command mode (step 52), and the fact is notified to the computer system 1.

When a password, which is registered in advance in the modem 2 and represents a technician who can perform a specific setting of the modem 2 in the second escape mode, is input by the technician and given to the modem 2 from the computer system 1. (YES in step 53), the modem 2 accepts the second escape second command setting command input by the engineer and given from the computer system 1 (step 54).

When the second escape second command setting command is given from the computer system 1 to the modem 2 (YES in step 55), the modem 2 executes the second escape second command change command, and thereby the second escape second command change command is issued. The escape second command is set (step 57).

Second Escape When a command other than the second command setting command and the password registered in advance is given from the computer system 1 to the modem 2 (NO in steps 53 and 55), the modem 2 causes the second escape
Mode to online mode (step 5
6) Notify the computer system 1 to that effect.

When the second escape second command is set, the modem 2 inputs the computer
The second escape second command given from the system 1 is accepted (step 58).

If the command matching the second escape second command set in step 57 is a computer
When given to modem 2 from system 1 (in step 59
(YES), the modem 2 starts after resetting the timer (step 60), and again accepts the second escape second command input by the technician and given from the computer system 1 (step 61).

If the command matching the second escape second command set in step 57 is a computer
When system 1 gives it to modem 2 again (step
62: YES), the command is the first escape
The modem 2 judges whether or not the command is given within a predetermined time after being given (step 63). When modem 2 determines that the second escape second command has been given within a predetermined time (YES in step 63), modem 2 accepts the command input by the technician and given from computer system 1 (step 65).

When a command other than the second escape second command is given from the computer system 1 to the modem 2 (NO in steps 59 and 62), or the second second escape second command is issued to the computer within a predetermined time.・ When the system 1 did not give to the modem 2 (step 63)
YES), the modem 2 returns from the second escape second mode to the online mode (step 64) and notifies the computer system 1 to that effect.

It is judged whether the command input by the user or the technician and given to the modem 2 from the computer system 1 conforms to a predetermined format (step 66). When it is determined that the command does not conform to the predetermined format (NO in step 66), the fact is notified to the computer system 1.

When the modem 2 determines that the command given from the computer system to the modem 2 is the return command (YES in step 67), the modem 2 returns from the second escape second mode to the online mode (step 67). 68), and notifies the computer system 1 to that effect.

When the modem 2 determines that the command given to the modem 2 from the computer system 1 is the line disconnection command (YES in step 69), the modem 2 disconnects the telephone line (step 71), and the command is issued. -Transition to the mode (step 72) and notify the computer system 1 to that effect.

When the command given from the computer system 1 is a command other than the return command and the line disconnection command, the modem 2 performs a process according to the command (step 70), and outputs the processing result to the computer system 1 Return to. The computer system 1 displays the processing result on the display device.

[Brief description of drawings]

FIG. 1 is a block diagram showing how two computer systems are connected via a modem and a telephone line.

FIG. 2 is a block diagram showing a detailed configuration of a modem.

FIG. 3 shows a state transition diagram of a mode of a modem.

FIG. 4 shows a connection state according to each mode of two computer systems and a modem.

FIG. 5 shows an example of an escape command. (A) shows a first escape command, (B) shows a second escape command, and (C) shows a second escape second command. .

FIG. 6 is a flow chart showing a processing procedure of a modem in a command mode.

FIG. 7 is a flow chart showing a processing procedure of the modem in the online mode.

FIG. 8 is a flow chart showing a processing procedure of a modem in a first escape mode.

FIG. 9 is a flowchart showing a processing procedure of a modem in a second escape mode.

FIG. 10 is a flowchart showing a processing procedure of the modem in the second escape mode.

FIG. 11 is a flowchart showing a processing procedure of a modem in a second escape mode.

[Explanation of symbols]

 1,4 Computer system 2,3 Modem 11 Interface circuit 12 CPU 13 Modulation / demodulation circuit 14 NCU 15 ROM 16 RAM

Claims (4)

[Claims] 1. A device for use, which is connected between a computer system and a telephone line network, and which includes a command input from the computer system in a state where the line is disconnected and including a command for starting communication. In the command mode for executing one type of command and in the state where the line is connected, the signal input from the computer system is modulated and transmitted to the telephone line network, and the signal input from the telephone line network is transmitted. An online mode that demodulates and gives to the computer system, and a first escape that executes a second type of command that is input from the computer system with a line connected and that includes a command relating to a change in communication parameters・ Mode,
And a second escape mode for executing a third type of command including a command relating to a change in communication parameters input from the computer system in a state where the line is connected, and an online mode A second escape command input from the computer system and including a first signal and a second signal of a predetermined length continuous at least immediately before or immediately after the first signal. To the second escape mode, and in the second escape mode, receives the third signal input from the computer system and the signal relating to the length thereof, and registers these signals, After that, the first signal and the at least one immediately before or after the first signal are continuously registered. Has been on condition that accepts and the third signal having the length, accept the third type of command is ready, mode switching method of the modem. 2. In the second escape mode, the third signal and the signal concerning its length are transmitted only when the password input from the computer system has a predetermined conflict with a predetermined password. The mode switching method of the modulation / demodulation apparatus according to claim 1, wherein the mode is ready for acceptance. 3. The first signal and the third signal having the registered length that continues at least immediately before or after the first signal are repeated a plurality of times within a predetermined time. The mode switching method of the modulator / demodulator according to claim 1, wherein the command of the third type can be accepted on condition that the command is accepted. 4. A computer which is used by being connected between a computer system and a telephone line network, and which includes a command input from the computer system in a state where the line is disconnected and a command for starting communication. In the command mode for executing one type of command and in the state where the line is connected, the signal input from the computer system is modulated and transmitted to the telephone line network, and the signal input from the telephone line network is transmitted. An online mode that demodulates and gives to the computer system, and a first escape that executes a second type of command that is input from the computer system with a line connected and that includes a command relating to a change in communication parameters・ Mode,
In the modulator / demodulator having: a second escape mode processing means for executing a third type of command including a command relating to a change of communication parameters, which is input from the computer system in a state where a line is connected,
And when in the online mode, the first signal input from the computer system and the first signal
And a mode switching means for activating the second escape mode processing means when a second escape command including a second signal of a predetermined length continuous immediately before or immediately after the signal is received. The second escape mode processing means receives a third signal inputted from the computer system and a signal concerning the length thereof and registers these signals, and thereafter, the first signal and the first signal. The command of the third type can be accepted on condition that the third signal having the registered length and continuing at least immediately before or after the first signal is accepted. A modulator / demodulator characterized by the following.