JPH06261147A - Terminal network controller - Google Patents

Abstract

PURPOSE:To provide a terminal network controller which can perform the communication at a high speed and has a wide range of applications. CONSTITUTION:A BPF part 24 extracts a signal of a 3rd frequency band including the 1st and 2nd frequency bands out of those signals received through each circuit in a reception mode. The extracted signal is amplified at an AC amplifier part 25 and then a 1st modulated wave in a 1st frequency band or a 2nd modulated wave in a 2nd frequency band is identified at a carrier-1 detecting part 27. Then a carrier signal of the 1st or 2nd modulated wave is detected at a carrier-2 detecting part 29. Based on these detection signals, a demodulation circuit part 26 performs the demodulation in response to each modulated wave. Meanwhile a modulation circuit part 28 performs the modulation in response to the 1st and 2nd modulated wave in a transmission mode. The signal is amplified at the part 25 and the unnecessary frequency components are eliminated through the part 24. Furthermore the high frequency components are eliminated through a smoothing filter part 31, and the signal is amplified at an AC amplifier part 30 and transmitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terminal network control device, and more particularly to a terminal network control device for connecting a communication line and a terminal device and controlling bidirectional data transmission using a plurality of modulated waves. It is a thing.

[0002]

2. Description of the Related Art Conventionally, an existing electric circuit network is used,
It is possible to read the measured values of the gas meter, water meter, electric power meter, etc. installed in the home without ringing the bell of the telephone in the home of the telephone user. This is a kind of data communication system in the no ringing communication service and is provided as a telemeter system. By this, the center side such as gas companies or water companies,
Since it is possible to automatically collect desired data when necessary, it is possible to solve the labor shortage in data meter reading. FIG. 12 is a schematic block diagram showing the configuration of a data communication system to which a conventional terminal network control device is applied.

In the data communication system of FIG. 12, the center unit 127 includes a host computer 110 and a center side network control unit (C-NCU) 111.
The network control device 111 on the center side is connected to the host computer 110 via a connection line 119, and is also connected to the center side telephone exchange station 112 via a telephone line 120. On the other hand, the terminal device 126 includes a terminal network control unit (T-NCU) 115, a terminal such as the meter 116, and a home telephone 118. Terminal network control device 115
Is the terminal-side telephone exchange station 113 via the subscriber telephone line 122.
It is connected to the. Also, each terminal of the meter 116 and the home telephone 118 is connected to the terminal network control device 115 via a connection line 123. Center side telephone exchange 1
12 and the terminal telephone exchange 113 are connected to each other by an interoffice relay line 121.

In the no ringing communication system, the network control device 1 on the center side is instructed by the host computer 110.
11 calls the no-ringing trunk 114 and holds it. Next, after the no-ringing trunk 114 reverses the polarity of the subscriber telephone line 122, a no-ringing call signal is given to the terminal network controller 115. When the no-ringing ringing signal is detected, the terminal network control device 115 controls the home telephone 118 so as not to ring the bell but to communicate with the meter 116, for example.

On the other hand, during automatic terminal transmission, when the terminal network control device 115 detects that a predetermined time has come, the terminal side network control device 115 moves the center side network control device 111.
Is automatically called. In this case, the meter reading information of the meter 116 indicates that the terminal network control device 115, the telephone line 122, the interoffice relay line 121 and the telephone line 120.
Also, it is transmitted to the host computer 110 via the network control device 111 on the center side. The host computer 110 performs data processing such as charge calculation and printout based on the received signal based on a predetermined program processing.

In the telemeter system adopting the above-mentioned no ringing communication system, a home telephone 118 and a meter 11 for meter reading are used as terminal devices in the consumer's home.
There are six. Switching of the connection between the telephone line 122 and the data terminal device is controlled by the terminal network control device 115. The terminal network controller 115 employed in this telemeter system normally operates so as to connect the home telephone 118 to the telephone line 122.

When operating as a telemeter system,
The terminal network control device 115 switches the connection of the telephone line 122 from the home telephone 118 side to the meter 116 side. That is, the terminal network control device 115 detects the vacant state of the home telephone 118 by inputting the on-hook signal of the telephone 118, and accordingly, the connection of the telephone line 122 is connected.
Side to the meter 116 side. Then, in accordance with a predetermined transmission control procedure, a call is made to the terminal and the like, the connection of the telephone line on the side of the center device 127 is established, and the meter 11
Meter reading data such as 6 is sent to the telephone line 122 and transmitted to the center device 127 side.

When collecting meter reading data in the meter 116 from the center device 127 side, the host computer 110 instructs the terminal network control device 115 to switch the connection of the telephone line 122 via the center side network control device 111. , The meter 116 side is controlled to transmit the meter reading data.

As described above, the terminal network controller 115
Operates to detect the vacant state of the communication line to be connected, switch the circuit connection, and send the data in the desired data terminal device to the connected line.

As described above, the center device 127
Since the terminal device 126 transmits desired data,
The terminal network control device 115 has a modem unit having a modulation or demodulation function for mutually converting digital signal data into an analog signal suitable for transmission. In general, the terminal network control device performs data communication according to a standard compliant with V21 of CCITT (International Telegraph and Telephone Consultative Committee), which is a standard for international data communication.

CCITT V21 adopts a full-duplex communication system capable of simultaneous bidirectional communication, and two communication modes, an answer mode and a call mode, can be set. The received signal used in the answer mode uses the mark signal of 980 Hz and the space signal of 1180 Hz, while the transmitted signal uses the mark signal of 1650 Hz and the space signal of 1850 Hz. Also, the mark signal of the received signal used for the call mode is 1650H.
z, the space signal is 1850 Hz, while the transmitted signal is
Mark signal is 980Hz, space signal is 1180Hz
Using the frequency of.

A conventional terminal network control device that realizes the above-mentioned CCITT V21 compliant specifications is provided with a modem section described below. FIG. 13 is a block diagram showing a configuration of a modem unit of a conventional terminal network control device.

The modem section includes an AC amplifier section 90, a filter section 91, a sample hold section 92, a low band BPF (band pass filter) section 93, a high band BPF section 94, an AC amplifier section 95, a carrier detection section 96, and a demodulation circuit section. 97, mode control unit 98, modulation circuit unit 99, smoothing filter unit 1
00, AC amplifier section 101, analog switch SW1
Including SW9.

First, the operation of the modem section upon reception will be described. Received signal from telephone line is RXA input terminal
Is input to the AC amplifier 90 and amplified to a predetermined level by the AC amplifier 90. The filter unit 91 and the sample and hold unit 92 form a low-pass filter of about 2.6 KHz, and remove the unnecessary band from the amplified received signal. On the other hand, mode terminal M
A command signal for commanding the answer mode or the call mode is input to the ODE and transmitted to the mode control unit 98. In the answer mode based on the command signal, the mode control unit 98 turns on the analog switch SW3, turns off the analog switch SW4, turns on the analog switch SW7, turns off the analog switch SW8, and the low-frequency BPF unit 9
Select 3. In the call mode, the analog switch SW3 is turned off, the analog switch SW4 is turned on, the analog switch SW7 is turned off, the analog switch SW8 is turned on, and the high frequency BPF section 93 is selected. Therefore, the output signal of the sample hold circuit 92 is output to the low frequency band BPF unit 93 in the answer mode and to the high frequency band BPF unit 94 in the call mode. The frequency band of the low band BPF section 93 is 900 to 1250 Hz, and the high band PBF is
The frequency band of 94 is 1600 to 1900 Hz. These frequency bands correspond to the frequencies of the mark signal and the space signal, and the signals of the required frequencies can be extracted. The reception signal from which unnecessary frequency components have been removed by the low band BPF unit 93 or the high band BPF unit 94 is amplified again to a predetermined value by the AC amplifier unit 95 and output to the carrier detection unit 96 and the demodulation circuit unit 97. The carrier detector 96 detects a carrier signal from the amplified received signal and outputs it to the carrier terminal CD. Demodulation circuit 9
7 demodulates the amplified received signal and outputs the mark signal as a logic 1
Then, the space signal is converted into a logic 0 and output as a digital signal to the reception output terminal RXD. The above conversion is FSK
(Frequency Shift Keying) This is based on the demodulation method.

By the above operation, the demodulation operation for demodulating the received signal which is an analog signal into a digital signal is completed.

Next, the operation of the modem section upon reception will be described. A logical signal that is a digital signal is transmitted to the transmission input terminal T
When input to the XD, the modulation circuit section 99 is modulated by the FSK modulation method into a transmission signal which is an analog signal of the predetermined frequency. The mode control unit 98 has a mode terminal M
Based on the ODE command signal, analog switch SW2,
By switching SW5, SW6, and SW9, the high band BPF unit 94 is selected in the answer mode, and the low band BPF unit 93 is selected in the call mode. Therefore, the modulated transmission signal is input to the smoothing filter unit 100 after passing through the high band BPF unit 94 or the low band BPF unit 93 to remove unnecessary frequency components. The smoothing filter unit 100 removes the high frequency component of the transmission signal again. The transmission signal from which the high frequency component has been removed is the AC amplifier unit 1
01 is amplified to a predetermined level and the transmission output terminal TXA
Is output to. By the above operation, the modulation operation for converting the transmission signal which is a digital signal into an analog signal is completed.

With the above configuration, the modem section can be operated by the full-duplex communication method capable of transmitting and receiving at the same time by switching the answer mode and the call mode.

[0018]

The terminal network control device is
In addition to the remote automatic meter reading as described above, the network control device of the home information terminal device can be applied to non-store sales, catalog shopping, collection of regional information, and the like. In this case, the amount of information to be transmitted becomes very large and a high speed communication function is indispensable. However, the conventional network control device for a terminal is a half-duplex communication system in which the transmission mode is fixed to the answer mode, the communication speed is limited to a low speed of 200 or 300 bps, and high-speed communication cannot be performed.

An object of the present invention is to solve the above problems, and it is an object of the present invention to provide a terminal network control device which enables high speed communication and has a wide range of application.

[0020]

A terminal network control device according to claim 1 modulates data of the terminal device into a first modulated wave within a first frequency band or a second modulated wave within a second frequency band. Modulating means, extracting means for extracting a signal in the third frequency band including the first and second frequency bands, and demodulation for demodulating the first or second modulated wave from the signal in the third frequency band extracted by the extracting means And means.

According to a second aspect of the present invention, there is provided a terminal network control apparatus, wherein the terminal means data is modulated into a first modulated wave in a first frequency band or a second modulated wave in a second frequency band, and a first modulating wave. Alternatively, the demodulation means for demodulating the second modulated wave into the original data, and the selection for selecting the first or second modulated wave as the modulated wave to be transmitted or received according to the error occurrence state of the data demodulated by the demodulating means And means.

[0022]

In the terminal network controller according to claim 1,
Since the extraction means can extract the signal in the third frequency band including the first and second frequency bands, the unnecessary frequency component is removed from the first and second modulated waves at the time of transmission or reception to remove the first frequency component.
And the second modulated wave or the first and second modulated waves can be demodulated.

In the terminal network control device according to the second aspect, the first or second modulated wave is selected according to the error occurrence state of the demodulated data, and the modulated wave suitable for the state of the transmission path is received. Or you can send it.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A terminal network control apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a terminal network control device according to an embodiment of the present invention. Each connection of the terminal network controller is shown in FIG.
This is the same as the conventional example shown in FIG.

In FIG. 1, the terminal network control device 1 is shown in FIG.
It is connected to a telephone line 122 shown in FIG. 2 and calls itself to communicate with other terminal devices or perform no ringing communication. Home telephone 118 shown in FIG.
Is connected to the telephone line 122 via the terminal network control device 1. A meter 116 shown in FIG. 12 is connected to the terminal network control device 1. The data of the meter 116 is transmitted to the center device 112 via the terminal network control device 1 after the telephone line link is established.

The terminal network control device 1 includes a station line circuit 2. The office line circuit 2 includes a polarity reversal detection circuit 3, a rectification circuit 4, a dial pulse circuit 5, an NRS detection circuit 6, and a half loop control circuit 7. The polarity inversion detection circuit 3 detects that the polarity of the DC voltage applied to the telephone line has been inverted from the current state to the opposite polarity. The rectifier circuit 4 includes, for example, a full-wave rectifier diode bridge, and converts the polarity of the DC voltage applied to the telephone line into a predetermined constant polarity regardless of its positive or negative polarity. The dial pulse circuit 5 sends a dial pulse to the telephone line in response to a command from the main control circuit 9. That is, the dial pulse circuit 5 puts a dial pulse on the telephone line by intermittently short-circuiting the telephone line. The NRS detection circuit 6 sends the NR sent from the no ringing trunk 114 shown in FIG.
The S signal is detected. As the NRS signal, for example, PB (push button) signals from 0 to 9 are used. The detection output of the NRS detection circuit 6 is the main control circuit 9
Given to. The half-loop control circuit 7 responds to a command from the main control circuit 9 in direct-current and alternating-current impedance of the telephone line in order to prevent the deterioration of the transmission characteristic due to the impedance imbalance during no ringing communication or automatic terminal transmission. Is maintained at a specified value of a predetermined technical standard.

The terminal network control device 1 further includes a main control circuit 9, an interface circuit 10, a reset circuit 15,
Oscillation circuit 14, power supply circuit 13, off-hook detection circuit 1
2, a connection switching circuit 11 and a modem unit 8 are included. The main control circuit 9 includes, for example, a microcomputer, and controls the operation of each circuit in the terminal network control device 1. The interface circuit 10 takes in the data output from the meter 116 shown in FIG. 12 and supplies it to the main control circuit 9. The reset circuit 15 is a circuit for resetting the main control circuit 9 when the terminal network control device 1 is activated from the initial state. The oscillator circuit 14 is a circuit for generating a timer clock signal that serves as a reference for the timekeeping operation in the main control circuit 9. The power supply circuit 13 is a circuit for supplying operating power to each circuit in the terminal network control device 1. The connection switching circuit 11 is a circuit for switching the connection state of the connection line connected to the home telephone 118 in response to a command from the main control circuit 9. That is, the connection switching circuit 11
The connection line is connected to the telephone line during normal operation, and is connected to the off-hook detection circuit 12 during no ringing communication or automatic terminal transmission. The off-hook detection circuit 12 detects whether or not the home telephone 118 is used during no-ringing communication or automatic terminal transmission. The detection output of the off-hook detection circuit 12 is given to the main control circuit 9. The modem unit 8 is provided for data communication between the terminal network control device 1 and the center device. That is, the modem section 8 modulates the data given from the main control circuit 9 and sends it to the center apparatus via the telephone line. Further, the modem unit 8 demodulates the data given from the center device via the telephone line and outputs it to the main control circuit.

Next, the modem section 8 which modulates or demodulates a transmission or reception signal in this apparatus will be described in detail. FIG. 2 is a block diagram showing the configuration of the modem unit 8.

The modem unit 8 includes an AC amplifier unit 21, a filter unit 22, a sample hold unit 23, a BPF (band pass filter) unit 24, an AC amplifier unit 25, and a demodulation circuit unit 2.
6, a carrier 1 detection unit 27, a modulation circuit unit 28, a carrier 2 detection unit 29, and analog switches SW10 to 13. The modem unit 8 has a CCITT V21-compliant 300 bps communication speed as well as a CCITT VIT.
It is configured to be able to communicate even at a communication speed of 1200 bps conforming to V23 of T. Therefore, this device can perform high-speed communication four times faster than the conventional one, and can be applied not only to the conventional remote automatic meter reading system, but also to storeless sales dealing with a large amount of data, catalog shopping, and the like.

First, the reception operation of the modem section 8 will be described in detail. As a reception signal to be used, an answer mode is used at a communication speed of 300 bps conforming to V21 of CCITT, and a mark signal is 980 Hz and a space signal is 1180 Hz. Also, V of CCITT
A signal having a mark signal of 1300 Hz and a space signal of 2100 Hz is used at a communication speed of 1200 bps conforming to H.23. As the demodulation system of the received signal, the same FSK demodulation system as the conventional one is used.

The transmission signal as described above is received by the reception input terminal R.
It is input to XA and amplified to a certain level by the AC amplifier section 21. The filter unit 22 and the sample hold 23 form a low pass filter, and remove unnecessary frequency components from the amplified received signal. On the other hand, a control signal is input to the mode terminal MODE from the above-mentioned main control circuit 9, and the mode control unit 32 uses the analog switch SW1 based on the control signal.
0, SW12 turned on, analog switches SW11, S
W11 is turned off and the sample hold unit 23 on the receiving side
And the BPF unit 24 are connected. The frequency band of the BPF unit 24 is about 900 to about 2200 Hz, and is set so that both the received signals of 300 bps or 1200 bps can be extracted. Therefore, the sample hold unit 2
The received signal output from 3 is about 900 to about 2200 Hz
The unnecessary frequency components other than
Is output to. The received signal amplified by the AC amplifier unit 25 to a predetermined level is input to the demodulation circuit unit 26, the carrier 1 detection unit 27, and the carrier 2 detection unit 29, respectively.

Next, the carrier 1 detector 27 will be described in detail. FIG. 3 is a block diagram showing the configuration of the carrier 1 detection unit 27. The carrier 1 detection unit 27 includes a comparator 40, a retriggerable one shot (retriggered monostable multivibrator) unit 41, and a comparator 4.
2, a threshold controller 43, a sampling clock unit 44, a capacitor 45, and a threshold generation unit 46, and constitutes an FV converter.

The comparator 40 compares the received signal output from the AC amplifier section 25 with the threshold level of the threshold controller 43 set to a predetermined output level in advance according to the clock signal of the sampling clock section 44. . After the comparison, if the level of the received signal is higher than the threshold level, it is input to the retriggerable one-shot unit 41, and the retriggerable one-shot unit 41 outputs a pulse having a predetermined pulse width in response to this input. . The comparator 41 compares the signal obtained by integrating this pulse with the capacitor 45 and the threshold level of the threshold generator 46 set to a predetermined output level in advance, and outputs it to the first carrier terminal CD1. FIG. 4 shows the carrier 1 detection unit 2 described above.
It is a figure which shows the output signal of FIG. As shown in FIG. 4, the output of the carrier 1 detector 27 has a frequency of an input signal of 1200
Until ~2400Hz is output at the level of V _DD, the V _DD corresponds to a logical 1, otherwise corresponding to a logical 0. As a result, since the frequency of the 300 bps mark signal is 980 Hz, the 300 bps mark signal is output as logic 0, and the 1200 bps mark signal frequency is 1300 Hz, so the 1200 bps mark signal is output as logic 1. Therefore, the carrier 1 detection unit 27 determines whether the mark signal of 300 bps is 1200 or not.
It is possible to identify whether the mark signal is bps.

Next, the carrier 2 detector 29 will be described in detail. FIG. 5 is a block diagram showing the configuration of the carrier 2 detection unit 29. The carrier 2 detection unit 29 includes a comparator 50, a retriggerable one-shot unit 51, a waveform shaper 52, a threshold controller 53, a sampling clock unit 54, and a capacitor 55.
It constitutes a -V converter.

The comparator 50 is the AC amplifier unit 2 of FIG.
The sampling clock unit 5 receives the received signal output from the signal No. 5 and the threshold level of the threshold controller 53 set to a predetermined output level in advance.
Comparison is made according to the clock signal of 4. After the comparison, the output of the comparator 50 is the retriggerable one-shot unit 5
1 is input and retriggerable according to this input signal.
The one-shot section 51 outputs a pulse having a predetermined pulse width. After this pulse is integrated by the capacitor 55, the waveform is shaped by the waveform shaper 52 and output to the second carrier terminal CD2. FIG. 6 is a diagram showing an output signal of the carrier 2 detector 29. As shown in FIG. 6, the carrier 2 detection unit 2
The output of 9 has an input signal frequency of 980 to 2400 Hz.
Otherwise the output at the level of V _DD, the V _DD corresponds to a logical 1, in the case of 980~2400Hz corresponding to a logical 0. Here, V _DD is output at 2400 Hz or higher because of the frequency characteristic of the BPF unit 24 described above. As a result, 300 bps and 1200 bps
Carrier signal (mark or space signal) is 980
Since there is .about.2100 Hz, both carrier signals are output as logic 0, and the others are output as logic 1. Therefore, it is possible to detect carrier signals of 300 bps and 1200 bps.

Next, the demodulation circuit section 26 will be described in detail. FIG. 7 is a block diagram showing the configuration of the demodulation circuit unit 26. The demodulation circuit unit 26 includes a comparator 61, a retriggerable one-shot unit 62, a sampling clock unit 63, a threshold controller 64, a comparator 65, resistors 66 to 73, a capacitor 74, a diode 75, a transistor 76, and an FV converter. Are configured.

Output from the AC amplifier section 25 shown in FIG.
The received signal has a DC component removed by the capacitor 74,
After a predetermined voltage divided by the resistors 66 and 67 is applied,
Predetermined voltage divided by resistors 68 and 69 in the comparator 61
Voltage reference voltage. Output after comparison is retriggered
Predetermined pulse input to the bull one shot unit 62
Converted to width pulses. This pulse is sampled
The lock unit 63 samples at a predetermined clock frequency
After that, it outputs to the comparator 65. Meanwhile, the threshold
The hold controller 64 is the carrier 1 detection unit 2 described above.
Identify whether the communication speed is 300 bps or 1200 bps with 7.
The main control circuit 9 and the mode control unit shown in FIG.
It is input via 32. Threshold control
The controller 64 is a threshold threshold corresponding to this communication speed.
The bell is output to the comparator 65. Sampling black
The received signal output from the clock unit 63 is sent to the comparator 65.
Is compared with the threshold level according to the communication speed.
Resistor 72, 73, diode 75, transistor
The waveform is shaped by the controller 76 and output. 300 bp in FIG.
The output of the demodulation circuit unit 26 at s is 1200 bps in FIG.
The output of each time is shown. As shown in FIG. 8, 300b
When ps is 1.08 kHz or less, V_DDOut at the level of
Forced, this V_DDCorresponds to logic 1, otherwise is logical
Corresponds to reason 0. Therefore, the mark signal of the received signal
(980Hz) to logic 1 and space signal (1180H
z) can be converted to logical 0 and restored to the original data.
Can be adjusted. Further, from FIG. 9, 1200 bps
In case of 1.7 V or less V _DDOutput at the level of
This V_DDCorresponds to a logical 1; otherwise, a logical 0
Corresponding to. Therefore, the mark signal (13
00Hz) to logic 1 and space signal (2100Hz)
Can be converted to logical 0 and demodulated to the original data
You can As described above, the demodulation circuit unit 26 has three
Can demodulate both 00 bps and 1200 bps
Is.

As described above, in the modem section 8, 1
After removing unnecessary frequency components from the received signal by one BPF unit 24, the carrier signal of the received signal is detected by the carrier 2 detection unit 29 to detect the transmission from the center device,
The carrier 1 detection unit 27 can identify the communication speed of the received signal. As a result, the demodulation circuit unit 26 can realize the demodulation operation according to the communication speed, and can send the received data to the main control circuit 9 shown in FIG. 1 to perform desired processing.

Next, the transmission operation of the modem section 8 will be described. The transmission signal used is V21 of CCITT
The answer mode is used at the communication speed of 300 bps conforming to the standard, the mark signal is 1650 Hz, and the space signal is 1
A signal of 850 Hz is used. Also, CCITT V23
A signal having a mark signal of 1300 Hz and a space signal of 2100 Hz is used at a communication speed of 1200 bps conforming to the standard. As the modulation method of the transmission signal, the same F
The SK modulation method is used.

First, the main control circuit 9 shown in FIG. 1 creates data to be transmitted and outputs it to the modem section 8. Modem section 8
In the inside, the data is sent to the transmission input terminal TXD and input to the modulation circuit unit 28. On the other hand, to the mode control unit 32, the communication speed command (300 bps or 1200 bp) is sent from the main control circuit 9 of FIG. 1 via the mode terminal MODE.
s) is sent, and the frequency oscillating unit (not shown) of the modulation circuit unit 28 is controlled according to this command. The frequency oscillating unit is 1300 Hz, 1650 Hz, 1850 Hz, 2100 corresponding to the frequency of the mark or space signal of each communication speed.
It has an oscillating unit of Hz. The modulation circuit unit 28 is 300b
In the case of ps, if the transmission data logic is 1, 1650 Hz,
If 0, output a frequency of 1850Hz, 1200bps
In the case of 1, the frequency of 1300 Hz is output when the logic of the transmission data is 1, and the frequency of 2100 Hz is output when the logic of the transmission data is 0, and the modulation operation is performed. At this time, the mode control unit 32 causes the analog switch S
W10, SW12 off, analog switch SW11,
Since the SW 13 is turned on, the modulated transmission signal is sent to the BPF unit 24, and unnecessary frequency components are removed. BPF
The transmission signal output from the unit 24 has the high frequency component removed again by the smoothing filter 31, and then the AC amplifier unit 3
After being amplified to a predetermined level at 0, the transmission output terminal TX
Output to A. The reception signal output from the transmission output terminal TXA is sent to the center device through the telephone line as in the conventional case.

With the above configuration, the modem section 8 is 300b
It becomes possible to perform transmission / reception operation at a communication speed of ps or 1200 bps.

Next, a communication sequence of the terminal network control device according to the present invention will be described with reference to a flowchart. FIG. 8 is a flowchart of the communication sequence. A program for executing this flowchart is stored in advance in a storage unit (not shown) of the main control circuit 9 shown in FIG. 1, and the main control circuit 9 reads and executes a predetermined program.

First, in step S1, the main control circuit 9 checks whether or not the reception flag is set.
The reception flag is a flag that is set when the transmission operation is completed. If this flag is not set, the reception operation cannot be performed, so the process proceeds to step S16, and if it is set, the process proceeds to step S2.

When the reception flag is set, in step S2, the main control circuit 9 causes the carrier 2 detector 2
It is checked whether the second carrier output terminal CD2 of 9 is logic 0. If the second carrier output terminal CD2 is logic 0, it indicates that the received signal is input, and therefore, step S3
Move to and continue processing. If the logic is 1, nothing has been received, and the process returns to step S1 to restart the process.

If the second carrier output terminal CD2 has a logic 0, the main control circuit 9 causes the carrier 1
It is checked whether the first carrier output terminal CD1 of the detection unit 27 is logic 0. When the first carrier output terminal CD1 is logic 0, the received signal of 300 bps has been input, and therefore the process proceeds to step S4 and it is confirmed whether or not the logic is changed. If there is a change, the process returns to step S1 to restart the process, and if there is no change, the process proceeds to S5, the receiving operation is performed at 300 bps, and the process is continued until the reception end is confirmed in step S6. The receiving operation detects the rising edge of the data input to the main control circuit 9 via the modem section 8,
The received data is sampled, the data is stored in the storage unit, and the process based on the data is executed. After the reception is completed, the process proceeds to step S7.

On the other hand, when the first carrier output terminal CD1 is logical 1, since the received signal of 1200 bps is input, the process proceeds to step S8 and is similar to step S10 and the above-mentioned steps S4 to S6. Perform processing. If the reception is not completed in step S10, the process proceeds to step S11 to check whether an error has occurred. If no error has occurred, the process returns to step S9 and steps S9 to S10.
repeat. If an error has occurred, step S1
At 2, the communication flag is set. In this case, the communication flag indicates that an error has occurred in 1200 bps communication. Next, in step S13, it is checked whether or not the second carrier output terminal CD2 is logic 0. While the logic is 0, that is, while the reception signal is being input, step S13
When the logic is 1, that is, the input is completed, the process proceeds to step S14 and the reception flag is reset. Next, in step S15, the center device is instructed to change the data so that the data is transmitted at 300 bps. this is,
This is because the center device is notified that data cannot be transmitted at high speed because the line quality is deteriorated, and the communication speed is reduced to improve the transmission quality and perform stable data transmission. After the instruction, the process returns to step S1 to continue the process again.

After confirming the reception end in step S10, it is confirmed in step S7 whether or not the communication is completed. If not completed, the process returns to step S1 to prepare for the next communication, and the process is performed again. to continue. If it has ended, it returns to another processing of the program and continues the processing.

If the reception flag is not set in step S1, the process proceeds to step S16 and the transmission process is performed. In step S16, it is confirmed whether the communication flag is set. As described above, the communication flag is a flag indicating that the line quality is poor and an error may occur. Therefore, if it is set, the process proceeds to step S20 to perform transmission at 300 bps.
If it is not set, a large amount of data can be sent in a short time if data is transmitted at high speed.
It moves to 17 and transmits at 1200 bps.

When transmitting at 1200 bps, in step S17, the main control circuit 9 rearranges the data to be transmitted in the storage unit into a predetermined format and outputs it as a serial signal of 0.83 ms per bit to the transmission input terminal TXD of the modem unit 8. Output. FIG. 11 shows a schematic diagram of a data transmission format. As shown in FIG. 11, the transmitted data has a format in which a mark signal is added to the head portion for a time T and then a message portion to be sent as data follows. This format is the same for both transmission and reception. After transmitting the data in the above format, it is checked in step S18 whether the transmission is completed. If not completed, the process returns to step S17 to send the next data. If it has been completed, the reception flag is set in step S19, and the process returns to step S1 to continue the processing again.

When the communication flag is set in step S16 and the process proceeds to steps S20 and S21, a serial signal of 300 bps, that is, 3.3 ms per 1 bit is transmitted by performing the same processing as steps S17 and S18. .

As described above, this apparatus can perform transmission or reception at two communication speeds, high speed and low speed, and at high speed, transmission and reception can be performed at four times the communication speed of the conventional one. Therefore, a large amount of data can be transmitted in a short time, and the application range of the device can be expanded. In addition, this device uses only one BPF section to
Since the transmission and reception are realized at one communication speed, the circuit configuration is simplified and the cost of the apparatus main body can be reduced at the same time.

Furthermore, since the present apparatus checks the error occurrence during high speed communication and switches to low speed communication, high speed communication can be enabled according to the transmission quality. This check function is not limited to the one having one BPF section as in the present embodiment, and the same effect can be obtained even if one having two or more BPF sections.

In the above embodiment, 300 bps and 1200
Although the bps communication speed has been described, the present invention is not limited to these communication speeds, and similar effects can be obtained for a desired communication speed.

[0054]

In the terminal network control device according to the first aspect of the present invention, it is possible to communicate at two communication speeds, and a large amount of data can be communicated at the time of high speed communication of one of them. Can be extended.

In the terminal network control device according to the second aspect, the first or second modulated wave is selected according to the error occurrence state of the demodulated data, and communication is performed with the modulated wave suitable for the state of the transmission path. Therefore, high-speed communication can be enabled according to the transmission quality, and the application range of the device can be expanded.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a terminal network control device of the present invention.

FIG. 2 is a block diagram showing a configuration of a modem unit of the terminal network control device of the present invention.

FIG. 3 is a block diagram showing the configuration of a carrier 1 detection unit of the modem unit of the terminal network control device of the present invention.

FIG. 4 is a diagram showing an output of a carrier 1 detection unit of a modem unit of the terminal network control device of the present invention.

FIG. 5 is a block diagram showing a configuration of a carrier 2 detection section of a modem section of the terminal network control device of the present invention.

FIG. 6 is a diagram showing an output of a carrier 2 detection section of a modem section of the terminal network control device of the present invention.

FIG. 7 is a block diagram showing a configuration of a demodulation circuit unit of a modem unit of the terminal network control device of the present invention.

FIG. 8 is a diagram showing an output of the demodulation circuit unit of the modem unit of the terminal network control device of the present invention at 300 bps.

FIG. 9 is a diagram showing an output of the modulation circuit section of the modem section of the terminal network control device of the present invention at 1200 bps.

FIG. 10 is a flowchart illustrating a communication sequence of the terminal network control device of the present invention.

FIG. 11 is a diagram showing a communication format of the terminal network control device of the present invention.

FIG. 12 is a block diagram showing a configuration of a data communication system to which a conventional terminal network control device is applied.

FIG. 13 is a block diagram showing a configuration of a modem unit of a conventional terminal network control device.

[Explanation of symbols]

 24 BPF section 26 Demodulation circuit section 27 Carrier 1 detection section 28 Modulation circuit section 29 Carrier 2 detection section

Claims (2)

[Claims] 1. A network control device for a terminal, which connects a communication line to a terminal device and controls data transmission or reception, wherein data of the terminal device is a first modulated wave or a second modulated wave within a first frequency band. Modulating means for modulating into a second modulated wave within a frequency band, extracting means for extracting a signal in a third frequency band including the first and second frequency bands, and a third frequency band of the third frequency band extracted by the extracting means. A terminal network control device including demodulation means for demodulating the first or second modulated wave from a signal. 2. A network controller for a terminal, which connects a communication line and a terminal device to control data transmission or reception, wherein the data of the terminal device is a first modulated wave or a second modulated wave within a first frequency band. Modulating means for modulating the second modulated wave within the frequency band, demodulating means for demodulating the first or second modulated wave into original data, and depending on an error occurrence state of the data demodulated by the demodulating means , A terminal network control device including a selecting means for selecting a first or second modulated wave as a modulated wave to be transmitted or received.