JP3136840B2 - Terminal network controller - Google Patents

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 connected to a telephone line and performing line connection detection.

[0002]

2. Description of the Related Art A conventional terminal network control device will be described with reference to FIGS. In FIG. 3, the terminal network control device 1 is connected to a telephone line 2 and a gas meter 3.
The terminal network control device 1 includes a line connection terminal 4 for connecting a telephone line 2 and a line termination unit 5 for terminating the telephone line.
A modem unit 6 for exchanging transmission / reception signals from the line termination unit 5, a DT detection unit 8 for receiving a signal from the line termination unit 5 and detecting a dial tone from the line, It comprises a modulation / demodulation unit 6, a carrier detection unit 7, and a control unit 9 that controls the DT detection unit 8 and controls communication with the gas meter 3.

Next, the operation in the above configuration will be described with reference to FIG.
An example in which the gas meter 3 makes a communication request to the terminal network control device 1 to perform communication will be described with reference to FIG. The gas meter 3 makes a communication request to the control unit 9 of the terminal network control device 1 when, for example, the meter reading date is once a month. Upon receiving the communication request, the control unit 9 secures a communication path for performing communication with a center (not shown). First, the control unit 9 controls the line termination unit 5 to terminate the telephone line 2. Then, the control unit 9 monitors an output signal from the DT detection unit 8 in order to detect a dial tone signal (hereinafter abbreviated as a DT signal) meaning that a selection signal from the telephone line 2 may be transmitted.
The control unit 9 controls the 400 Hz D received from the telephone line 2.
When the T signal is detected, the control shifts to transmission control of the selection signal. For example, when the selection signal type of the telephone line is a dial pulse, the control unit 9 controls the line terminating unit 5 to close and open the line to transmit the dial pulse.

Next, the control unit 9 enters a communication start waiting state with a center (not shown). The control unit 9 monitors an output signal of the carrier detection unit 7 for detecting a signal in a frequency band of data communication (for example, a signal of 1080 ± 100 Hz in the case of the FSK system of 300 BPS). When detecting an output signal with a data signal from the carrier detection unit 7, the control unit 9 monitors input / output signals of the modulation / demodulation unit 6. Then, the control unit 9 outputs the digital signal received from the modem unit 6 to the gas meter 3. Conversely, a digital signal received from the gas meter 3 is transmitted to the telephone line 2 via the control unit 9, the modulation / demodulation unit 6, and the line termination unit 5, and transmitted to a center (not shown). When the communication end is received from the center, the control unit 9 sets the line termination unit 5 to the open state and returns to the standby state.

If communication is not established or does not end normally, the gas meter 3 performs a retry process for retrying communication, and the number of retries in a city gas meter is 30 or more.

Next, a line connection detection method in the conventional terminal network control device 1 will be described with reference to FIG.
When the control unit 9 detects that the terminal network control device 1 is connected to the telephone line 2, it monitors the output signal of the DT detection unit 8. The DT detection unit 8 detects a DT signal using frequency separation. While the frequency of the DT signal transmitted from the telephone line 2 is 400 Hz, the frequency of the communication signal for performing data communication is 1 here.
080 ± 100 Hz (generally, a frequency of 1 kHz or more).

FIG. 4A shows the DT signal and the data signal in the time domain. FIG. 4
The horizontal axis of-(a) represents the time axis, the vertical axis represents the voltage value, the DT signal is the frequency fo (Hz), and the data signal is the frequency fl (Hz). On the other hand, FIG.
-(A) is represented in the frequency domain. Fig. 4-
The horizontal axis of (b) represents frequency, and the vertical axis represents energy amount. In the DT detection unit 8, if the signal input from the line termination unit 5 passes through the filter having the band X shown in FIG. Is output, an output signal with a DT signal is output. On the other hand, when the data signal having the frequency fl is input to the DT detection unit 8, after passing through the filter having the band X, the data signal does not have the energy equal to or more than a certain value, and is output as having no DT signal.

[0008] Similarly, the carrier detector 7 has a fundamental operation principle of frequency separation. That is, when the data signal of the frequency fl passes through the carrier detection unit 7, the data signal has energy equal to or more than a certain value in the band Y.
Output when there is a carrier signal. On the other hand, when the DT signal of the frequency fo is input into the carrier detection unit 7 from the line, it is output that there is no carrier signal because the band Y does not have energy of a certain value or more.

[0009]

However, the above-mentioned conventional configuration has the following problems.

1) It is necessary to use a dedicated integrated circuit for detecting the DT signal, which increases the cost.

2) If the communication is performed without detecting the line connection, the battery power of the terminal network control device which is battery-driven when the telephone line is not connected is not only unnecessarily consumed but also disabled. You will fall. In general, a terminal network control device for automatic meter reading of a gas meter is generally installed in order from a newly built house, and in the case of a newly built house, a telephone line is connected until a resident applies for a telephone subscription. This is caused by not connecting on the exchange side.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a terminal network control device capable of detecting a telephone line connection by a simple method at a low cost.

[0013]

In order to achieve the above object, the present invention provides a line connection terminal for connecting a telephone line, a line termination unit for terminating the line connection terminal, and a connection to a line termination unit. A gain switching unit for switching the degree of amplification of a signal from the telephone line, a carrier detection unit for detecting a data communication signal input from the gain switching unit, and a line termination unit for terminating the gain of the gain switching unit. And a control unit for determining a line connection by monitoring an output signal from the switching carrier detection unit.

[0014]

According to the present invention, when the connection of the telephone line is detected, the control section terminates the line termination section, and the signal inputted to the line termination section is inputted to the carrier detection section via the gain switching section. Then, the control unit determines the line connection by monitoring the output of the carrier detection unit.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2, the line connection terminal 4
, A line termination unit 5, a modem unit 6, and a carrier detection unit 7.
Represents the same components as in the conventional example, and the description is omitted. On the other hand, the gain switching unit 10 switches the amplification degree of the signal input from the line termination unit 5 according to a command from the control unit 11,
The control unit 11 controls the line termination unit 5, the gain switching unit 10, the modulation / demodulation unit 6, and the carrier detection unit 7, controls the communication signal from the gas meter 3, and detects the connection of the telephone line.

Next, the operation of the above configuration will be described. The operation when performing communication for performing automatic meter reading from the gas meter 3 will be described. When there is a communication request from the gas meter 3 to the control unit 11 of the terminal network control device 9, the control unit 11 shifts to an operation for securing a communication path with a center (not shown). First, the control unit 11 terminates the line termination unit 5 and determines whether a line is connected. After terminating the line termination unit 5, the control unit 11
Is set larger than that of the communication channel. Then, a signal from the telephone line 2 is input to the carrier detection unit 7 via the telephone line 2, the line termination unit 5, and the gain switching unit 10. On the other hand, the control unit 11 determines whether the telephone line 2 is connected by monitoring the output signal of the carrier detection unit.

When the control unit 11 detects that the telephone line 2 is connected, the control unit 11
A gain of 0 is switched for communication. After that, the control unit 11 via the line termination unit 5, the gain switching unit 10, and the modem unit 6
Digital signal is input to the gas meter 3
Transmitted to the side. Similarly, the signal from the gas meter 3 is
The signal is output to the telephone line 2 via the control unit 11, the modulation / demodulation unit 6, the gain switching unit 10, and the line termination unit 5.

On the other hand, if the control unit 11 determines that the terminal network control device 9 is not connected to the telephone line 2, the control unit 11
Ignores the communication request from the gas meter 3 and stops the operation for securing the communication path. This prevents the battery of the terminal network control device 9 driven by the battery power from being unnecessarily consumed.

Next, the principle of connection detection of the telephone line 2 will be described with reference to FIGS. The following contents are used when the control unit 9 determines the connection of the line.

1) When the telephone line 2 is connected,
When the line is terminated, the DT signal is received by the terminal network control device 9, but when the telephone line 2 is not connected, no signal is received.

2) The carrier detector determines that there is a carrier signal when there is energy of a predetermined value or more in a predetermined frequency band.

3) When the gain of the operational amplifier constituting the gain switching section is increased, the output signal is saturated with the power supply voltage.

4) When the square wave is viewed in the frequency domain, it contains a harmonic component of the fundamental frequency. First, a case where the telephone line 2 is connected to an exchange will be described. Since the control unit is in a mode in which the connection of the telephone line 2 is determined, the telephone line 2 is terminated by the line terminating unit 5 and the gain switching unit 1
The gain of 0 is set large. The control unit 11
Monitors the output signal from the carrier detector 7. Since the telephone line 2 is connected, the terminal network control device 9 receives the DT signal, and at the input point A of the gain switching unit 10, the waveform shown in the upper part of FIG. 2 is observed in the time domain and the frequency domain. Is done. The signal at point A is
0, the signal is amplified to the extent that the signal is saturated.
At the output point B of 0, the waveform is as shown in the lower part of FIG.

That is, the signal at point B is completely saturated and becomes a square wave when viewed in the time domain, and has an energy distribution including harmonics of the fundamental frequency when viewed in the frequency domain. The signal at point B is input to the modem unit 6. As described in the conventional example, when the input signal to the modulation / demodulation unit 6 has energy equal to or more than a certain value in the band Y in FIG. 2, the output with the carrier signal is performed. On the other hand, the gain switching unit 1
The DT signal from the line which has become a square wave at 0 has energy within a band Y of a certain value or more as shown in the lower frequency region of FIG. Therefore, the output of the carrier detector 7 has a carrier signal. The control unit 11 determines that the telephone line 2 is connected by detecting the presence of a carrier signal by the carrier detection unit 7.

Next, a case where the telephone line 2 is not connected (connected to the exchange) will be described. When the telephone line 2 is not connected, even if the line termination unit 5 is terminated, the telephone
No signal is received from. Therefore, the gain switching unit 1
Even when the signal passing through 0 is viewed in the frequency domain, the output of the carrier detection unit 7 is output as "no carrier signal" because the band Y has no energy equal to or greater than a certain value. The control unit 11 determines that the telephone line 2 is not connected since the output of the carrier detection unit 7 indicates that there is no carrier signal.

That is, the DT signal is received only when the telephone line 2 is connected, and the signal is saturated by the gain switching unit 10 to generate a higher harmonic wave, which is fixed in the detection frequency band of the carrier detection unit 7. The control section 11 monitors the presence of the carrier signal of the carrier detection section 7 by generating energy equal to or more than the value, thereby determining the connection of the telephone line 2.

According to the configuration of this embodiment, when determining the connection of a line, the control unit 11 terminates the line termination unit 5 and is input to the gain switching unit 10 in a high gain state.
When a telephone line is connected, a square wave is output,
When the telephone line is not connected, no signal is output. Therefore, when the telephone line is connected, the modulation / demodulation unit outputs that there is a carrier signal, and when it is not connected, it outputs that there is no carrier signal. That is, the control unit 11 monitors the output of the carrier detection unit 7 to determine whether the telephone line is connected. Therefore, the control unit 11 does not use the DT detection unit as in the related art.
There is an effect that the line connection can be detected at low cost.

[0028]

As described above, in the terminal network control device of the present invention, when making a line connection determination, the control unit terminates the line termination unit and is input to the gain switching unit in a high gain state. A square wave is output when the telephone line is connected, and no signal is output when the telephone line is not connected. Therefore, when the telephone line is connected, the modulation / demodulation unit outputs that there is a carrier signal,
When the telephone line is not connected, it outputs that there is no carrier signal. That is, the control unit monitors the output of the carrier detection unit to determine whether or not the telephone line is connected, so that the line connection can be detected at low cost without using the DT detection unit as in the related art. There is.

[Brief description of the drawings]

FIG. 1 is a block diagram of a terminal network control device according to an embodiment of the present invention.

FIG. 2 is a signal waveform diagram of each unit shown in FIG. 1 of the apparatus.

FIG. 3 is a block diagram of a conventional terminal network control device.

FIG. 4A is a waveform diagram of the same device shown on a time axis, and FIG. 4B is a waveform diagram of the same device shown on a frequency axis.

[Explanation of symbols]

 Reference Signs List 5 Line termination unit 7 Carrier detection unit 9 Terminal network control device 10 Gain switching unit 11 Control unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04M 1/00 H04M 1/24-1/253 H04M 1/58-1/62 H04M 1/66-1 / 82 H04M 3/02-3/06 H04M 11/00-11/10 H04M 19/00-19/08

Claims (1)

(57) [Claims] A line connection terminal for connecting a telephone line; a line termination unit for terminating the line connection terminal; a gain switching unit connected to the line termination unit for switching the amplification of a signal from the telephone line; A carrier detection unit for detecting a data communication signal input from the gain switching unit; a line termination unit for terminating the line termination unit to switch a gain of the gain switching unit; and monitoring an output signal from the carrier detection unit to determine a line connection. Terminal network control device, comprising: