JP3361548B2 - Communication equipment with transmission line loss calculation function - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device having a transmission line loss calculation function, and in particular, it measures the incoming level of a tone signal output from a switchboard to obtain a signal attenuation amount of the transmission line, Based on this, each set value is changed to an optimum value.

[0002]

2. Description of the Related Art Recently, information devices such as personal computers, facsimiles and word processors for transmitting information using a telephone line have rapidly spread, and have become widespread as an information transmitting means instead of mail.

By the way, these information devices must generally meet the technical standards for connecting to an analog line. When conforming to this technical standard, setting communication parameters in consideration of line conditions, for example, transmission line loss and transmission distance between the information equipment terminal and the exchange as much as possible will ensure more reliable communication. Becomes important.

Therefore, there is a need for means for automatically recognizing line conditions and automatic rewriting control for various parameters in order to eliminate communication troubles due to line conditions and ensure reliable communication. Among the technical standards for information equipment terminals that connect to analog lines in countries around the world, including Japan, are those that specify standard values at the connection part (output end from the terminal) between the terminal and the communication line, and the There are two types, one that defines the standard value in the input part.

In the former case, when each standard value is set at the output end from the terminal, whether or not the standard is satisfied depends on the terminal itself. There is no need to reset various parameters.

On the other hand, when the standard values are set in the input section of the latter exchange, it is very likely that a serviceman or a user resets various parameters registered at the time of terminal installation to optimum values. There are many.

By the way, when changing each parameter to an optimum value at the time of installing a terminal, conventionally, a person in charge of construction who has a qualification for telephone construction calls the nearest telephone office and a single tone is sent from the exchange to the terminal. (In Japan, a sine wave of 1500 Hz) is sent, and the incoming level of that tone is measured at the installation site to obtain the signal attenuation amount of the transmission line.

Then, based on this measured value, the value of the signal transmission level from the terminal is changed to the optimum value, and various parameters are reset based on the approximate distance to the exchange. In addition, recently, since general electronics stores and mass retailers handle these devices for the purpose of expanding the information equipment to the home market and mass-selling, it is up to the user who purchased the terminal to set the parameters, and some trouble. When a problem occurs, it is becoming mainstream to deal with the problem by a service call.

[0009]

Considering, for example, a facsimile in an information device, in a currently popular mainstream thermal recording machine and in a plain paper facsimile which has recently become mainstream, a serviceman sets various parameters when a terminal is installed. It is common to reset the settings or change the settings at the time of periodic maintenance of the terminal.

When a communication trouble or the like occurs in these terminals, the user contacts the service person in charge, and the service person goes to the place where the terminal is installed to investigate the cause and deal with it. It is customary.

On the other hand, since a service person rarely attends a terminal purchased at a general electric appliance store or a mass retailer, each parameter registered in the terminal remains the same as the factory default even after the terminal is installed.

Therefore, when the standard value of the technical standard is determined according to the input condition to the exchange like the signal transmission level in Japan, it is premised that the distance between the exchange and the installed terminal is 0 km. Is set at the time of factory shipment. Therefore, the distance between the actually installed terminal and the nearest exchange is significantly different from the standardized 0 km.

Therefore, during long-distance communication in Japan or overseas communication, many image errors may occur in the received document, or communication troubles such as the inability to receive signals during communication may occur. . Therefore, it is an object of the present invention to provide a communication device capable of automatically recognizing installation conditions and automatically rewriting various parameters registered in a terminal.

[0014]

In order to achieve the above object, in the present invention, as shown in FIG.
A U unit 11, a level adjusting unit 12, a tone detecting unit 13, and a control unit 14 are provided. The NCU unit 11 connects and disconnects with the communication line 2 and recognizes a calling signal from the exchange 1. The level adjusting unit 12 amplifies the level of the received signal.
Attenuator, tone detector 13 is a single tone or MF
The (multi-frequency) tone is detected, and the control unit 14 controls the overall operation of the terminal 10.

[0015]

Operation: The control unit 14 sends the communication line 2 to the NCU unit 11.
When an instruction signal for connecting the
The switching circuit inside the CU unit 11 is switched from the telephone side to the terminal side to form a DC loop.

When the exchange 1 recognizes that the terminal 10 has formed a DC loop, it sends a continuous sine wave (dial tone) of 400 Hz to the terminal 10. This dial tone is input to the level adjusting unit 12 via the NCU unit 11. The level adjuster 12 gradually attenuates the signal level of the input dial tone according to an instruction from the controller 14, and inputs it to the tone detector 13.

At this time, the level adjusting unit 12 attenuates to the limit detectable by the tone detecting unit 13, and the control unit 14 recognizes the amount of attenuation in the level adjusting unit 12 at this time. Now, the signal detection range that the tone detection unit 13 can detect is 0 to −
In the case of 43 dBm, a signal level of -43 dBm can be detected, but a signal level of -44 dBm cannot be detected.
Therefore, when the tone detection unit 13 has attenuated to the limit that can be detected, the control unit 14 recognizes the signal level input to the tone detection unit 13 at this time as -43 dBm.

At this time, the attenuation amount of the level adjusting unit 12 is Ln dB, and the attenuation amount of the NCU unit 11 is 0, that is, the input signal level of the terminal 10 is equal to the input signal level of the level adjusting unit 12. For example, the control unit 14 sets the incoming signal level of the input terminal A of the terminal 10 to-(43-Ln).
It can be calculated as dBm. Then, since the signal attenuation amount of the transmission line can be calculated by this, various parameters of the terminal 10 can be automatically set based on this.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 shows an example of the level adjusting section. In FIG. 2, the same reference numerals as those in the other drawings indicate the same parts, 15 is a telephone, 16 is an amplifier circuit, 1
Reference numeral 7 is a bandpass filter, 18 is a waveform conversion circuit, 19 is a memory, 20 is a line equalizer setting unit, and 21 is a timer.

The NCU unit 11 connects / disconnects with the communication line 2 according to an instruction from the control unit 14 or detects a call signal (16 Hz in Japan) from the exchange 1 to the terminal 10 and notifies the control unit 14 of the signal. Alternatively, the image information is transmitted / received to / from the partner terminal through the NCU unit 11.

The NCU section 11 is provided with a switching circuit 11-1, a transformer circuit 11-2, a correction amplifier circuit 11-3, a modem circuit 11-4, a loop detection circuit 11-5 and the like. The switching circuit 11-1 performs switching such as connecting the communication line 2 to the telephone side or connecting to the terminal side.
The correction amplifier circuit 11-3 is for automatically setting the signal transmission level, and the value of the signal attenuation amount is set to the modem circuit 11-.
4 is added to the output of 4 to automatically set the signal transmission level.

The amplifier circuit 16 corrects the amount of attenuation of the signal transmitted from the communication line 2 in the NCU unit 11 so that the signal level at its output terminal B is at the same level as the terminal A of the signal transmitted from the communication line 2. It is something to do. That is, the signal input level of the level adjuster 12 is made equal to the input level of the terminal A.

The level adjusting section 12 is for attenuating or amplifying the received signal that has passed through the NCU section 11 in accordance with an instruction from the control section 14, and is constructed, for example, as shown in FIG. FIG. 3A shows that the resistors R1 to Rn are individually selected according to the instruction of the control unit 14 and the gain thereof is adjusted, and FIG.
The gain is adjusted by selecting one of each pair from 1 to rm.

The bandpass filter 17 and the waveform conversion circuit 18 are for detecting the frequency of 400 Hz sent from the exchange 1.
A signal frequency of 00 Hz is extracted and this is converted into a waveform conversion circuit 18
Waveform shaping by.

The memory 19 stores the gain of the amplifier circuit 16 in accordance with the values of the resistors R1 to Rn in the case of FIG. 3 (A), and each pair of resistors r1 to rm in the case of FIG. 3 (B). The gain of the amplifier circuit 16 is stored according to the selected combination of. If this is used, a specific calculation can be omitted.

Next, the operation of the present invention will be described. The communication line 2 is connected to the terminal at the terminal A, and is connected to the telephone 15 inside the terminal via the switching circuit 11-1. Now, when the switching circuit 11-1 is switched from the telephone 15 side to the terminal side, the communication line 2 is connected to the transformer circuit 11-2, and the exchange-communication line 2-transformer circuit 11-2 forms a DC loop.

The detection of this DC loop formation is carried out by the loop detection circuit 11-5, which makes it possible to detect the hook of the telephone set 15, the loop of the terminal having the automatic calling function, and the polarity of the line. become. The loop detection circuit 11-5 notifies the control unit 14 of this loop detection.

As described above, when the switching circuit 11-1 is switched to the transformer circuit 11-2 side to form a DC loop, the exchange 1 sends a continuous sine wave (dial tone) of 400 Hz to the terminal. come. This dial tone is input to the amplifier circuit 16 via the switching circuit 11-1 and the transformer circuit 11-2.

By the way, the transformer circuit 11-2 transmits / receives data.
It is composed of a hybrid transformer for separating each received signal, and a resistor and a capacitor to satisfy return loss. This causes the signal to be attenuated as it passes through these circuits, so that the input level at terminal A and terminal B
Transformer circuit 11 to equalize the signal levels at
The output of −2 is amplified by the amplifier circuit 16.

The signal amplified by the amplifier circuit 16 is transmitted to the tone detector 13 via the level adjuster 12-bandpass filter 17-waveform converter 18. The tone detection unit 13 notifies the control unit 14 of the presence or absence of this signal detection as a status signal.

When the tone detector 13 notifies that the signal is detected, the controller 14 instructs the level adjuster 12 to perform level down control. As a result, the level adjusting unit 12 changes the feedback resistance value so as to attenuate the predetermined attenuation amount, for example, 1 dB. As a result, when the tone detector 13 notifies that the signal is detected, the controller 14 further instructs the level adjuster 12 to perform level down control. This is performed until the tone detection unit 13 notifies that no signal has been detected.

The tone detection section 13 has a predetermined signal level of a detectable tone. The signal detection range is now 0-4
In the case of 3 dBm, a signal level of −43 dBm can be detected, but a signal level of −44 dBm cannot be detected, so tone detection is possible when the level attenuation amount in the level adjusting unit 12 is Ln, and tone detection is possible when the level attenuation amount is Lm. If not detectable, it can be determined that the output level of the level adjusting unit 12 is −43 dBm when the level attenuation amount is Ln.

Therefore, the signal level L _B at the terminal _B is L _B
= -43 + Ln. Further, the signal at the terminal A is attenuated by the attenuation amount G in the switching circuit 11-1 and the transformer circuit 11-2, and then amplified by the amplification amount G by the amplification circuit 16 and output to the terminal B. When the signal level is L _A , L _B = L _A. Therefore, L _A =-
43 + Ln. In this way, the signal level L _A at the terminal A can be known.

On the other hand, the signal output level L ₀ from the exchange 1
Because are determined at a constant value of the known signal attenuation An of a communication line (transmission line) can be obtained by calculation from An = L ₀ -L _A.

Further, using the signal attenuation amount thus obtained, the modem circuit 11-4 set at the time of terminal shipment is set.
The value of the transmission level setting of the signal output from can be changed by the correction amplification circuit 11-3.

As in Japan, the factory shipment value of the signal transmission level of the terminal connected to the analog line is -15 dB.
In the case of m or less, the signal level reaching the exchange 1 becomes lower due to the attenuation of the signal in the communication line 2 as it is.

According to the technical standard, since the input level to the exchange 1 may be -15 dBm or less, it is optimal to send the signal from the terminal so that the input end of the exchange is -15 dBm from the certainty of communication. . Therefore, it is more effective to set the value in which the set value of the transmission level is increased by the amount of attenuation calculated by the terminal in order to ensure reliable communication.

The control unit 14 controls the line equalizer setting unit 20 based on the signal attenuation amount thus obtained, and sets the set value of the line equalizer, which is one of the parameters affecting the signal transmission level and the modulation / demodulation of the signal. Can be changed automatically.

Further, by periodically using the timer 21 to measure the signal attenuation amount, installation conditions and external conditions, for example, changes in line conditions due to replacement of terminals due to moving, construction of telephone lines, etc. Also, it becomes possible to obtain stable communication performance. In order to periodically perform this measurement operation, for example, a registration period holding unit 14-1 may be provided instead of the timer, and a period may be registered for this period such as one month or three months.

[0040]

As described above, according to the present invention, the terminal connected to the communication line automatically measures the incoming level of the tone transmitted from the exchange, and the signal attenuation amount of the transmission line is determined from the measured value. By the calculation, even if the standard value of the technical standard is determined in the input condition of the exchange, the optimum value for communication can be set in the terminal.

Further, this level measurement is periodically performed, for example, 1
If it is done automatically once a month or once every three months, it will be possible to change parameters automatically due to external conditions, such as changes in the laying of telephone cables and changes in the installation location of terminals. It will be very useful and useful for communication.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

FIG. 3 is an example of a level adjusting unit in the present invention.

[Explanation of symbols]

1 exchange 2 communication lines 10 terminals 11 NCU department 12 Level adjuster 13 Tone detector 14 Control unit

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04M 3/26 H04B 3/06 H04B 3/46 H04N 1/00

Claims (2)

(57) [Claims] 1. A switching means for controlling connection and disconnection between a terminal and a communication line, and a communication device for measuring an incoming level of a tone signal sent from a partner terminal or an exchange, the level of the incoming tone signal is attenuated. The level adjusting means, the tone detecting means for detecting the tone signal output from the level adjusting means, and the controlling means are provided, and the controlling means can detect the tone signal sent from the exchange by the tone detecting means. A communication device having a transmission line loss calculation function up to the exchange and its own terminal based on the amount of attenuation in the level adjusting means and the signal detection range of the tone detecting means after recognizing the amount of attenuation after being attenuated to the limit. . 2. The measuring means periodically measures the incoming call level, and based on the result of the measurement , a signal transmission level or a signal conversion level.
The communication device according to claim 1 , further comprising a control unit that rewrites a setting value related to a key .