JPH0263247A - Control system for data terminal equipment - Google Patents

Abstract

PURPOSE:To prevent the occurrence of over-correction of a line characteristic by a cable equalizing circuit in the case of connecting the data terminal equipment to an extension by inserting the cable equalizing circuit in the case of the connection to an external line and by not inserting the cable equalizing circuit in the case of the connection to the extension after the establishing of line. CONSTITUTION:The cable equalizing circuit 7 to correct the line characteristic due to a nonloaded cable connecting the data terminal equipment between terminal stations is inserted between other changeover connection terminal 4b of a switch 4 and other changeover connection terminal 6b of a switch 6. Then after the establishment of line, the cable equalizing circuit 7 is inserted in the case of connection to an external line and the cable equalizing circuit 7 is not inserted in the case of connection to an extension. Since the cable equalizing circuit 7 is used in the case of connection to the external line only, the occurrence of over-correction of the line characteristic by the cable equalizing circuit 7 in the case of connection to the extension is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control system for a data terminal device that can be selectively connected to either an outside line or an extension line.

[Prior Art] A data terminal device, such as a facsimile machine, which uses an analog line as a transmission path may be connected to a private branch exchange or a dedicated line to transmit data between extension lines.

Even when connected to an extension in this way, a general-purpose facsimile device that uses the public telephone network as a transmission path is used as the facsimile device.

[Problems to be Solved by the Invention] However, when a facsimile device connected to a so-called outside line is connected to an extension line as is, the following problems have conventionally occurred.

In other words, in a facsimile machine connected to an outside line, a cable equalizer is inserted between the modem and the line in order to compensate for the attenuation between the terminals of the unloaded cable used in the public telephone line. .

On the other hand, extension lines have very little attenuation like unloaded cables.

For this reason, when a facsimile device connected to an outside line is used as an extension line, the cable equalizer inserted between the modem and the line may overcorrect the line characteristics, resulting in a problem of deterioration of transmission quality.

SUMMARY OF THE INVENTION An object of the present invention is to solve these conventional problems and provide a control method for a data terminal device that can be appropriately connected to both an outside line and an extension line.

[Means for Solving the Problems] The present invention includes a line switching means for selectively connecting either an external public telephone line or an extension line, and a cable equalization circuit for improving the characteristics of the external line.

When establishing a line, a cable equalization circuit is inserted when connecting to an outside line, but no cable equalization circuit is inserted when connecting to an extension line.

[Function] Therefore, since the cable equalization circuit is used only when connecting to an outside line, over-correction of line characteristics by the cable equalization circuit is prevented when connecting to an extension line.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows the main parts of a data terminal device according to an embodiment of the present invention. Note that, in this figure, parts of the data terminal device that are not particularly related to the present invention are omitted.

In the figure, outside lines such as public telephone networks are shown.

It is connected to one switching connection end AI, A2 of the two-circuit line switching device 1, and the extension line of a private branch exchange is connected to the other switching connection end Bl, 82 of the line switching device I. The common connection ends C1 and C2 of 1 are connected to the primary side of a transformer 2 for cutting off the 5 lines and this data terminal equipment in terms of direct current, and the secondary side of this transformer 2 is connected to the 2 lines 7.
It is connected to the 2-wire side input terminal of the 4-wire converter 3.

The received signal output end of the 2-wire/4-wire converter 3 is connected to the common connection @@4c of the switch 4, and the transmitted signal input end is
It is connected to the transmission signal output end of the modem 5 that performs modulation and demodulation processing for data transmission.

The received signal input end of the modem 5 is connected to a common connection end 6c of a switch 6, and one switch connection end 6a of this switch 6 is connected to one switch connection end 4a of the switch 4. There is.

Further, between the other switching connection end 4b of the switching device 4 and the other switching connection end 6b of the switching device 6, line characteristics due to an unloaded cable connecting this data terminal device between the terminal stations are corrected. A cable equalizer circuit 7 is inserted for this purpose.

Further, the outside line paging signal detector 8 detects a paging signal output when an outside line calls this data terminal device, and the detection signal S1 is a control signal that controls the overall operation of this data terminal device. It has been added to Part 9.

The extension ringing signal detector 10 detects a ringing signal output when an extension calls this data terminal device, and its detection signal S2 is applied to the control section 9.

The mtm unit 9 receives the control signal s3. s4. s5 controls the switching operations of the line switching device 1 and switching devices 4 and 6, respectively. Note that the control unit 9 also controls other control elements in the data terminal device.

With the above configuration, the control section 9 normally controls the line switching device 1° and the switching devices 4 and 6 to the neutral position.

In this state, as shown in FIG. 2, the control unit 9 monitors whether the outside line ringing signal detector 8 or the extension ringing signal detector 10 performs a detection operation and either the detection signal Sl or S2 is applied. (No loop of process 101).

Here, if this data terminal device makes a call (the result of judgment 101 is YES) and the detection signal S1 is output from the outside line paging signal detector 8 at that time (the result of judgment 102 is YES), the control unit 9 outputs the control signal S3 to cause the line switching device 1 to select the switching connection terminals AI and A2, and also outputs the control signal S4. S5 is output to make the switching devices 4 and 6 select the switching connection ends 4b and 6b, respectively (process 103
).

As a result, this data terminal device is connected to the outside line, and a cable equalizer circuit 7 for correcting line characteristics of the outside line is inserted between the outside line and the modem 5.

Then, the control unit 9 starts data reception using the outside line (process 104).

Further, if this data terminal device makes a call (the result of judgment 101 is YES) and the detection signal S2 is output from the extension paging signal detector 10 at that time (the result of judgment 102 is No), the control unit 9 outputs the control signal S3.

The line switch l selects the switching connection terminals Bl and B2, and the control signal S4. S5 is output to cause the switching devices 4 and 6 to select the switching connection ends 4a and 6a, respectively (process 105).

As a result, this data terminal device is connected to the extension line, and at this time, the cable equalizer circuit 7 for correcting line characteristics of the outside line is not inserted between the outside line and the modem 5.

In this case, the control unit 9 starts data reception using the extension (process 104).

In this way, in this embodiment, when a call is made from an outside line and data is transmitted using the outside line.

The insertion of a cable equalizer circuit 7 between the line and the modem 5 compensates for the attenuation caused by the unloaded cable connecting the end station and this data terminal equipment, thereby ensuring proper signal conditioning. Data transmission can be performed with

In addition, when a call is made from an extension line and data is transmitted using the extension line, the cable equalizer circuit 7 is not inserted, so when an extension line with good line quality is used, a situation where the characteristics are over-corrected is prevented. Data transmission using extensions can be performed appropriately.

Incidentally, in the above-mentioned embodiment, explanation has been given only at the time of reception, but when the cable equalizer circuit is used also at the time of transmission, the same processing as described above is performed.

That is, when making a call to an outside line, a cable equalizer circuit is inserted between the line and the modem.

Do not insert a cable equalizer circuit when calling an extension.

Note that in the above description, descriptions of parts not directly related to the present invention are omitted.

By the way, as the distance between the terminal station and the data terminal device increases, the resistance value of the unloaded cable connecting the terminal station and the data terminal device increases, and the attenuation characteristics of the line by the unloaded cable change.

Therefore, for example, as shown in FIG. 3(a), as the distance between the terminal station and the data terminal equipment increases, the line characteristics change with the curves CVI, CV2, . CV3. CV4(7), and the deterioration of the characteristics in the high frequency portion becomes greater.

As described above, since the line characteristics due to the unloaded cable change, the characteristics of the cable equalizer circuit inserted between one line and the modem must also be changed in accordance with the line characteristics.

In other words, the line characteristics are curves CVI and CV2°C, respectively.
V3. When in the state of CV4, the characteristics of the cable equalizer circuit are expressed as tffl(b)L, - curve DVI
, DV2. DV3° Set as shown in DV4.

Conventionally, the characteristics of such a cable equalizer circuit have been adjusted by a service person measuring the resistance value of the line at the time of li1 of the data terminal equipment, and adjusting it according to the measured value. 6 In addition, the line characteristics with an unloaded cable are , is determined by the distance from the terminal station, so the characteristics of the cable equalizer circuit need only be adjusted once when the data terminal equipment is installed.

Now, in recent years, with the spread of facsimile machines, facsimile machines for personal use have come to be provided.

This kind of facsimile machine.

When purchased at a store, individuals are responsible for installing and using the device at home, and cannot perform various settings that a service person would do at the time of installation.

Therefore, in such a facsimile machine, it is necessary for the user to adjust the characteristics of the cable equalizer circuit by himself, but it is difficult for the user to make such adjustment.

FIG. 4 shows the main parts of a facsimile apparatus according to another embodiment of the present invention to eliminate such inconveniences. In addition, in the figure, other elements are omitted from illustration.

In the figure, lines L1 and L2 are connected to the primary side of a transformer 13, with line L1 via dial relay 11 and line L2 via current detection circuit 12.

The secondary side of the transformer 13 is connected to a 2-wire 74-wire converter 14, and the received signal output end of the 2M/4M converter 14 is connected to the modem 1 via a receiving cable equalizer circuit 15.
It is connected to the received signal input terminal of 6. Also, modem 1
The transmission signal input terminal of 6 is connected to the transmission signal input terminal of the 2-wire/4-wire converter 14.

The current detection circuit 12 detects the current value flowing through the lines Ll and L2, and the detection signal SL is sent to the comparator #1.
17 is output.

The comparison circuit 17 determines which of a plurality of predetermined ranges the magnitude of the detection signal Si applied from the current detection circuit 12 falls within, and the determination output signal Sd is output from the receiving cable. It is output to equalizer circuit N15.

The reception cable equalizer circuit 15 corrects the line characteristics due to the unloaded cable, and has a plurality of line correction characteristics. Further, the line correction characteristic is determined by the determination output signal Sd output from the comparator circuit 17.

The ringing signal detector 18 is for detecting ringing signals applied via the lines Ll and L2, and its detection signal S10 is applied to the control section 19 that controls the facsimile machine.

Control unit 19 controls on/off of dial relay 11 using control signal Sll.

With the above configuration, when this facsimile machine makes a call and a ringing signal is added, the ringing signal detector 18 outputs a detection signal SIO to the control section 19.

As a result, the control unit 19 turns on the dial relay 11 using the control signal Sll, thereby causing one line Ll, L
Two DC loops are formed. At this time, lines Ll, L
The magnitude of the current flowing through the facsimile device 2 is determined by the resistance value of the unloaded cable stretched between the facsimile machine and the terminal station, and therefore, the larger the length of the unloaded cable, the smaller the value.

As a result, the current detection circuit 12 outputs a current detection signal Si corresponding to the current value flowing through the lines Ll and L2 at that time.

The comparison circuit 17 determines the stage of the current values of the lines Ll and L2 based on the current detection signal Si, and outputs a determination output signal Sd corresponding to the determination result to the reception cable equalizer circuit 15.

As a result, the characteristics of the receiving cable equalizer circuit 15 are set to a state that corrects the line characteristics due to the unloaded cable at that time.

Therefore, the received signal is inputted to the received signal input terminal of the modem 16 after the line characteristics due to the unloaded cable have been corrected, so that the modem 16 can appropriately analyze the received signal.

In this way, when the line is established, the characteristics of the receiving cable equalizer circuit 15 are set in a manner that corresponds to the line characteristics of the unloaded cable, so even if the user directly attaches the facsimile machine, special installation settings can be made. It is very easy to use because it does not require any configuring work.

Current detection circuit 12. An example of the comparison circuit 17 and the receiving cable equalizer circuit 15 is shown in FIG.

In the current detection circuit 12, two photocouplers Pct
, PC2's light emitting diodes LEDI, LED2 are arranged in opposite directions and are connected in parallel to the line L2, and the photocoupler Pct, the outputs of the respective phototransistors PTI, PT2 of PC2 are interconnected,
A signal at the interconnection end is output as a current detection signal Si.

In the comparison circuit 17, the current detection signal Si is passed through the comparator C
MI, CM2. It is added to one side input terminal of CM3.

Further, reference values RFI, RF2, and RF3 for classifying the current values of the lines L1 and L2 into four levels are added to the + side input terminal of the comparator CHI (1:M2.CH2).

Here, the magnitude of the current value flowing through the lines LL and L2 is usually about 20 to 100 mA.
It is classified into four levels: mA or more and less than 60 InA, and 20 mA or more and less than 40 mA. Therefore, the reference value RFI, RF2
．． RF3 has a current value of 100mA and 60mA, respectively.
, 40+oA.

Therefore, the current value flowing through lines LL and L2 is 100m
A or more, and if the frequency characteristics caused by the unloaded cables of lines Ll and L2 become the characteristics of the curve CVI in Figure 3 (a), the value of the current detection signal Si is larger than the reference value RFI, so the comparison Output signals S21°S22. of CMI, CH2, CH2. All of S23 are at logic L level.

When the current value is 6 ( Since the value is between the reference value RFI and the reference value RF2, the output signal S21 of the comparator CM1 becomes logic 1.
Comparator CM2. CM3 output signal S22. S
23 goes to logic L level.

When the current value is 40+aA or more and less than 60mA, and the frequency characteristic caused by the unloaded cable of 1°L2 becomes the characteristic of curve CV3 in Figure 3 (a), the value of the current detection signal Si is the standard. Since the value is between the value RF2 and the reference value 1'lF3, the output signals 521. of the comparators CMI and CM2.
When S22 is at logic I (level), the output signal S of comparator CM3
23 goes to logic L level.

1 line L when the current value is 20mA or more and less than 40a+A
l.

When the frequency characteristic caused by the unloaded cable of L2 becomes the characteristic of curve CV4 in Fig. 3(a), the current detection signal S
Since the value of i becomes smaller than the reference value RF3, comparators C old, CM2 . CM3 output signal 521. S22. Both S23 are at logical H level.

These output signals S21, S22 . S23 is applied to the reception cable equalizer circuit 17 as a determination output signal Sd.

The receiving cable equalizer circuit 17 includes an inverting amplifier OP whose cutoff frequency in a high frequency region is set, capacitors CCI, CC2, CC3, and 1 connected in parallel to an input resistor RI of the inverting amplifier OP, and this capacitor CCI. , CC2, CC3, and switches Svl, SW2, and 5Ii3 for turning on and off the connections.

Further, the switches SWI, SW2, and 5113 respectively control the signals S21. of the determination output signal Sd. S22. It is turned on when S23 is at a logic H level and turned off when it is at a logic L level.

Therefore, the current value flowing through lines LL and L2 is 100+
For nA or more, comparators CHI, C8 as described above
4, CH2 output signal S21. S22. Both S23 become logic L level.

As a result, switches SWI, SW2 . Since both SW3 are turned off, the characteristics of the receiving cable equalizer circuit 15 become as shown by the curve DVI in FIG. 3(b).

In addition, the current value flowing through lines Ll and L2 is 60 mA or more1
00 mA, as described above, the output signal S21 of the comparator CM1 goes to logic H level, and the output signal S21 of the comparator CM2. CM3
The output signal S22, 323 becomes a logic L level, which turns on the switch 5lll and turns on the switch SW2.
, 5IJ3 is turned off.

As a result, the capacitor CCI is connected in parallel to the input resistor RI, so that the characteristics of the receiving cable equalizer circuit 15 at this time are as shown by the curve DV2 in FIG. 3(b).

Also, if the current value flowing through lines Ll and L2 is 40mA or more6
If it is less than 0mA, the comparators CMI, CM
2 output signal 521. S22 becomes a logic H level, and the output signal S23 of the comparator CM3 becomes a logic L level, thereby turning on the switches 5ll and SW2 and turning off the switch SW3.

As a result, the capacitors CCI and CC2 are connected to the input resistor RI.
are connected in parallel, the characteristics of the receiving cable equalizer 15 at this time will be the characteristics of the song AIDV3 in FIG. 3(b).

Furthermore, if the current value flowing through one line Ll, L2 is 20 mA or more and less than 40 mA, the comparators CMI, C
M2°CH2 output signal S21. S22. S23 are both at logic H level, thereby causing the switch S
WI, SV2°SW3 are all turned on.

As a result, the capacitors CCI and CC2 are connected to the input resistor RI.
゜Since CC3 is connected in parallel, the characteristics of the receiving cable equalizer circuit 15 at this time are as shown by the curve D in FIG. 3(b).
It has characteristics similar to V4.

In this way, the frequency characteristics caused by the unloaded cables of lines Ll and L2 become curve CVI in FIG. 3(a).

CV2. CV3. When the characteristics of the receiving cable equalizer circuit 15 become the characteristics of CV4, the characteristics of the receiving cable equalizer circuit 15 correspond to the curves DVI, DV2. DV3. To become like DV4,
Signal degradation caused by unloaded cables can be appropriately corrected.

By the way, in this embodiment, the cable equalizer circuit is inserted only on the receiving side, but it is also possible to insert the cable equalizer circuit on the transmitting side. In such a case, the characteristics of the cable equalizer circuit on the transmitting side will also be the same as described above. Similarly, line Ll.

It is changed according to the current value of L2.

Further, in this embodiment, the characteristics of the cable equalizer circuit are changed in four stages, but the types of stages to be changed are not limited to these.

Furthermore, although this embodiment is applied to a facsimile machine, it can also be similarly applied to other data terminal equipment that uses a public telephone line network as a transmission path.

[Effects of the Invention] As explained above, according to the present invention, there is provided a line switching means for selectively connecting either the external public telephone line network or an extension line, and cable equalization for improving the characteristics of the external line. When a single line is established, a cable equalization circuit is inserted when connecting to an outside line, and a cable equalization circuit is not inserted when connecting to an extension line. This has the effect of preventing over-correction of line characteristics caused by

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main parts of a data terminal device according to an embodiment of the present invention, FIG. 2 is a flowchart showing an example of processing of the device in FIG. 1, and FIG. FIG. 4 is a graph diagram showing an example of line characteristics; FIG. 5B is a graph diagram showing characteristics of a cable equalizer; FIG. 2 is a circuit diagram showing an example of a current detection circuit, a reception cable equalizer circuit, and a comparison circuit. FIG. 1... Line switching, 4, 6... Switching device, 7... Cable equalizer circuit, 8... Outside line calling signal detector, 9
...control unit, 10...extension ringing signal detector. Figure Figure

Claims (1)

[Claims] Equipped with line switching means for selectively connecting to either the external public telephone line or an extension line, and a cable equalization circuit to improve the characteristics of the external line. A control method for a data terminal device characterized in that a cable equalization circuit is not inserted when connecting to an extension line.