JPH11252297A - Facsimile equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the facsimile equipment that conducts characteristic setting of an equalizer or the like without the need for a labor for the setting and not relying on an opposite facsimile equipment. SOLUTION: A modem 2 sends a high frequency test signal to a line with an instruction of a control section 1 in the facsimile equipment provided with equalizers 3, 4 and the test signal is made to wraparound at 2 line-4 line- conversion section 7 and a comparator circuit 9 receives a wraparound signal reflecting a line impedance with a frequency characteristic. When a level (b) of the wraparound signal is equal to or less than a comparison voltage (c), the equalizers 3, 4 output a signal with a higher level at a high frequency band and when the signal level (b) is greater than the comparison voltage (c), a signal with a level smaller than the above level at the high frequency band and larger than the level of the lower frequency band is outputted through the changeover of circuit constants of the equalizers 3, 4 by equalizer changeover sections 5, 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication apparatus such as a facsimile apparatus provided with an equalizer for correcting the frequency characteristic of a transmission / reception signal. In particular, it is possible to set a correction characteristic of an equalizer without relying on a counterpart facsimile apparatus. The present invention relates to a facsimile machine.

[0002]

2. Description of the Related Art Facsimile machines and telephones are connected to a public telephone network by subscriber lines. Since the subscriber line is essentially a low-pass filter, the high-frequency signal has a greater signal level attenuation at the receiving side than the low-frequency signal. For such reasons, facsimile apparatuses and the like have conventionally provided an equalizer to correct the frequency characteristics of a transmission signal and a reception signal. That is, for example, in the case of a transmission equalizer, the output level of the transmission signal is set to increase as the frequency increases (see FIG. 12). Since the attenuation in a high frequency band increases as the length of the subscriber line increases, it is desirable to set the correction characteristics of the equalizer according to each subscriber line. Therefore, in the method of V34 recommendation,
The attenuation amount (deterioration amount) of the transmission signal is obtained on the reception side, the result is notified to the transmission side, and the correction characteristics of the transmission equalizer on the transmission side are set. In a facsimile apparatus disclosed in Japanese Patent Application Laid-Open No. 4-127773, information on the amount of attenuation is stored in association with a destination, and a correction characteristic of a transmission equalizer is automatically set in accordance with the destination, and a signal level is set. Has been corrected. Further, as another conventional technique, an average value of attenuation is obtained from measured lengths of a large number of subscriber lines and the correction characteristics (frequency characteristics) of the equalizer are fixed, and the line resistance measured for each individual subscriber line is measured. (Equivalent to the length of the subscriber line), etc., the equalizer is used when it is better to use the above equalizer.

[0003]

However, in the above-described prior art in which the line resistance is actually measured for each individual subscriber line to determine whether or not to use the equalizer, a great deal of labor is required for the determination. Further, the method of the V34 recommendation has a problem that the correction characteristic of the transmission equalizer cannot be set depending on the function of the other party's facsimile apparatus. Further, in the prior art disclosed in Japanese Patent Application Laid-Open No. 4-127773, it is necessary to manually grasp the amount of attenuation of the reception signals of a large number of other facsimile apparatuses and manually notify the transmitting side by hand. Requires a great deal of effort. An object of the present invention is to solve the above-described problems of the prior art, to set a correction characteristic of an equalizer without requiring much labor for setting a correction characteristic of an equalizer, and without relying on a facsimile apparatus of the other party. It is an object of the present invention to provide a facsimile apparatus capable of performing such operations.

[0004]

According to the first aspect of the present invention, a test signal is transmitted to a line in a facsimile apparatus provided with an equalizer for correcting frequency characteristics of a transmission / reception signal. Test signal transmitting means, frequency characteristic measuring means for receiving a wraparound signal of the test signal transmitted by the test signal transmitting means and measuring its frequency characteristic, and a transmission equalizer according to the frequency characteristic measured by the frequency characteristic measuring means Alternatively, a correction characteristic setting means for setting a correction characteristic of the reception equalizer is provided. According to the second aspect of the present invention, in the above, the test signal transmitting means is configured to transmit a test signal having a plurality of types of predetermined frequencies, and a reception signal between the plurality of wraparound signals corresponding to the plurality of frequencies is provided. The frequency measuring means is configured to measure whether or not the signal level ratio is equal to or more than a predetermined value, and the transmission equalizer or the reception equalizer is turned on or off depending on whether or not the level ratio is equal to or more than a predetermined value. The correction characteristic setting means is constituted. According to a third aspect of the present invention, in the first aspect of the present invention, the test signal transmitting means is configured to transmit a test signal having one type of predetermined frequency, and the reception of the wraparound signal of the predetermined frequency is performed. The frequency measuring means is configured to measure whether or not the signal level is equal to or lower than a predetermined value.If the signal level is equal to or lower than the predetermined value, the transmission equalizer or the reception equalizer is turned on. The correction characteristic setting means is configured to perform the correction characteristic setting.
In a facsimile apparatus provided with an equalizer for correcting frequency characteristics of a transmission / reception signal, a plurality of transmission equalizers or reception equalizers having different correction characteristics, and a test signal for transmitting a test signal to a line side. Transmitting means, frequency characteristic measuring means for receiving a wraparound signal of the test signal transmitted by the test signal transmitting means and measuring its frequency characteristic, and transmitting the plurality of transmission signals in accordance with the frequency characteristics measured by the frequency characteristic measuring means Equalizer selecting means for selecting an optimum transmission equalizer or reception equalizer from among the equalizer or the reception equalizer.

[0005]

According to the first aspect of the present invention, the test signal is transmitted to the line side, and the frequency characteristic of the wraparound signal of the test signal reflecting the frequency characteristic of the attenuation in the line is measured. The correction characteristics of the transmission equalizer or the reception equalizer are set according to the measured frequency characteristics. According to a second aspect of the present invention, in the first aspect of the present invention, a test signal including a plurality of types of predetermined frequencies is transmitted, and a plurality of test signals corresponding to the plurality of frequencies and reflecting frequency characteristics of attenuation in a line are reflected. It is determined whether or not the received signal level ratio between the wraparound signals is equal to or greater than a predetermined value (or equal to or less than a predetermined value), and the transmission equalizer or the reception equalizer is determined based on whether or not the level ratio is equal to or greater than a predetermined value (or equal to or less than a predetermined value). It is turned on or off. According to a third aspect of the present invention, in the first aspect of the present invention, a test signal having one type of predetermined frequency is transmitted, and reception of the sneak signal of the predetermined frequency reflecting a frequency characteristic of an attenuation amount in a line is reflected. It is measured whether or not the signal level is equal to or lower than a predetermined value. If the signal level is equal to or lower than the predetermined value, the transmission equalizer or the reception equalizer is turned on. According to the fourth aspect of the present invention, the test signal is transmitted to the line side, the frequency characteristic of the wraparound signal of the transmitted test signal is measured, and an optimum one among a plurality of transmission equalizers or reception equalizers is measured according to the measured frequency characteristic. The appropriate transmission equalizer or reception equalizer is selected.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration block diagram of a main part of a facsimile apparatus showing a first embodiment of the present invention. As shown in the figure, the facsimile apparatus of this embodiment includes a control unit 1 for performing facsimile transmission / reception control and a test signal transmission instruction, a modem 2 for performing modulation of a facsimile transmission signal, demodulation of a reception signal, transmission of a test signal, and the like. The transmission equalizer 3 corrects the signal level according to the frequency of the received transmission signal, the reception equalizer 4 corrects the signal level according to the frequency of the reception signal, and the transmission equalizer switches the circuit constants of the transmission equalizer 3 to set the correction characteristics. A switching unit 5, a reception equalizer switching unit 6 for switching the circuit constants of the reception equalizer 4 and setting the correction characteristics,
A 2-wire to 4-wire conversion unit 7 for performing 4-wire conversion, a network control unit (NCU) 8 for performing line connection control and the like, a comparison circuit 9 as frequency characteristic measuring means for comparing the level of a wraparound signal with a comparison voltage, and the like. Have. The control unit 1 has a ROM with a built-in program, a CPU that operates according to the program, and the like. As is apparent from the above description, the test signal transmitting means is composed of the control unit 1 and the modem 2, and the correction characteristic setting means is composed of the control unit 1 and the equalizer switching units 5 and 6. FIG. 2 shows the details of the 2-wire to 4-wire conversion unit 7 and the NCU 8. As shown in the figure, the 4-wire side (the left side in the figure) is provided with an input terminal for receiving a transmission signal S from the transmission equalizer 3 and an output terminal for outputting a reception signal R to the reception equalizer 6. The transmission signal S is amplified by the amplifier 11 and transmitted to the telephone line via the line transformer 13 and the NCU 8. The received signal from the telephone line enters the amplifier 12 via the NCU 8 and the line transformer 13, and
2 and output as a received signal R. In FIG. 2, reference symbol R1 is a terminating resistor.

FIG. 3 shows an operation flow of the first embodiment. The operation of this embodiment will be described below with reference to FIG. The operation flow shown in FIG. 3 is executed when the user instructs the operation when the facsimile machine is installed. That is, the user instructs the equalizer setting by a method such as pressing a predetermined key in an operation unit (not shown) or selecting from a displayed menu. According to the above instruction, the control unit 1 instructs the modem 2 to transmit a test signal of a predetermined frequency, and the transmission equalizer switching unit 5 sets the transmission equalizer 3 to the off state (pass state) so as to output the input signal as it is. To instruct. The number of frequencies is, for example, a frequency originally provided in the modem 2 as a frequency for modulating facsimile image information. Thus, the modem 2 transmits a test signal of a predetermined frequency, for example, a sine wave for a predetermined time (S
1), the transmission equalizer 3 passes the test signal received from the modem 2 to the 2-wire to 4-wire conversion section 7 as it is. Then, the test signal is amplified by the amplifier 11 and transmitted to the telephone line via the line transformer 13 and the NCU 8, and the voltage at the point a (see FIG. 2) is changed by the resistor R1 and the primary impedance of the line transformer 13. The divided voltage is input to the amplifier 12 as a loop signal. The primary side impedance is proportional to the secondary side impedance of the line transformer 13, and the secondary side impedance is an impedance when the line side is viewed from the secondary side. For example, if the station side is terminated with 600Ω. , 300H
About 1000Ω at z, about 500Ω at 3400Hz
It is. However, the secondary side impedance also depends on the length of the subscriber line. For example, the impedance at 3400 Hz decreases as the length of the subscriber line increases. Also, when the subscriber line becomes longer, the amount of attenuation of a high-frequency signal on the signal receiving side (station side in the above example) increases. Therefore, when the frequency of the test signal is, for example, 3400 Hz, which is a high frequency, and the primary impedance in proportion to the secondary impedance becomes small,
Since the partial pressure decreases and the sneak signal decreases accordingly, it can be considered that the attenuation of the high-frequency signal increases. The present invention measures the level of the sneak signal of a high-frequency test signal using such a principle, and if the value is equal to or less than a predetermined value, it is considered that the amount of attenuation is large, and the equalization is performed in the high frequency region of the equalizer. Is to be increased.

Therefore, the sneak signal output from the amplifier 12 is input to the comparison circuit 9 and its voltage (level) b is compared with a predetermined comparison voltage c. The comparison circuit 9 is configured such that, for example, when the voltage b becomes equal to or higher than the comparison voltage c, the output becomes High level, and the control unit 1 monitors the output voltage of the comparison circuit 9 for a predetermined time. It is determined whether or not the output voltage is always at the low level (= the amount of attenuation is large). In this way, the frequency characteristic (signal level in a high frequency region) of the wraparound signal (received signal) is determined (S2),
If the output voltage of the comparison circuit 9 remains at the low level,
Assuming that the amount of attenuation is large (S2, A), a circuit constant of A is set in the transmission equalizer 3 (or the reception equalizer 4) (S3). On the other hand, if the output voltage of the comparison circuit 9 sometimes goes high during monitoring, it is considered that the amount of attenuation is small (S2, B), and the circuit constant of the transmission equalizer 3 (or the reception equalizer 4) becomes B. It is set (S4). In the above description, setting the circuit constant means selecting the value of the capacitor, resistor or inductor in the equalizer, and as shown in FIG. 4, the inverter 14 and the two transistors Tr1 and Tr1 as shown in FIG.
When the selection signal d output from the control unit 1 is at the High level, the transmission equalizer switching unit 5 (or the reception equalizer switching unit 6) comprising the transistor T
Turn on r1 and select, for example, capacitor C1,
When the selection signal d is at the low level, the transistor Tr2
Is turned on, for example, the capacitor C2 is selected.

Thus, the transmission equalizer 3 having the transfer characteristics (correction characteristics) as shown in FIG.
(Or the reception equalizer 4), so that, for example, in the case of the transmission equalizer 3, when the attenuation at the high frequency in the subscriber line is large at the time of the subsequent transmission, a higher level in the high frequency band is obtained. A signal is output from the transmission equalizer 3, and when the attenuation is relatively small, a signal of a slightly higher level is output in a high frequency band, and the attenuation can be appropriately corrected. Since the attenuation in the high-frequency region of the subscriber line occurs in the same manner at the time of reception, the circuit constant of the reception equalizer 4 can be similarly set, and the facsimile signal at the time of reception can be corrected. At the time of transmission, correction is made before the occurrence of attenuation in anticipation of attenuation. On the other hand, at the time of reception, the signal with attenuation is corrected and restored. In the second embodiment of the present invention, instead of setting the correction characteristics of the equalizers 3 and 4, the equalizers 3 and 4 are turned on when the amount of attenuation is large, and turned off (pass state) when the amount of attenuation is small. Thus, the transfer characteristics (correction characteristics and frequency characteristics) of the equalizers 3 and 4 are as shown in FIG.
In FIG. 6, C is a transfer characteristic when the equalizers 3 and 4 are on, and D is a transfer characteristic when the equalizers 3 and 4 are off. That is, when the amount of attenuation is large, the equalizers 3 and 4 are turned on,
Otherwise, it is turned off.

FIG. 7 shows the configuration of the equalizer of this embodiment. As shown in the figure, the equalizer switching units 5 and 6 are provided with two semiconductor switches Sw1 and Sw2. In the ON state, Sw1 is turned on and Sw2 is turned off. The transfer characteristics shown are realized, and in the off state (pass state), Sw1 is turned off and Sw2 is turned on, and the signal bypasses the equalizer circuit 15 to obtain the transfer characteristic indicated by the symbol D in FIG. In the third embodiment of the present invention, a plurality of transmission equalizers and a plurality of reception equalizers are provided, and different equalizers are selected according to the amount of attenuation instead of setting the correction characteristics of the equalizers 3 and 4, so that the equalizers 3 and 4 are equalized. The transfer characteristic of No. 4 is, for example, as shown in FIG.

FIG. 8 shows the configuration of the equalizer of this embodiment. As shown in the figure, two semiconductor switches Sw1 and Sw2 are provided in the equalizer switching units 5 and 6, which constitute equalizer selecting means together with the control unit 1, and the switch Sw1 is turned on,
When w2 is turned off, a signal is supplied to the first equalizer 3a (or 4a), Sw1 is turned off, and Sw is turned off.
2 is turned on to supply a signal to the second equalizer 3b (or 4b). As described above, in the first to third embodiments, the number of selections of the correction characteristic (transfer characteristic) of the equalizer is two, but in the fourth embodiment, the number of selections is three or more. For example, in the case of selecting a circuit constant, a decoder 16 is provided as shown in FIG.
Of the output D1, D2, D3 of the decoder 16 according to the value of
1, one of the capacitors C1, C2, and C3 is selected by turning on one of the transistors Tr2 and Tr3. Further, as shown in FIG. 10, the voltage (level) b of the sneak signal is changed to two comparison voltages c1, c2 (c1
<C2), for example, if the voltage b <c1, the capacitor C1 (FIG. 9) is selected, and c1 <b <c2
If it is, C2 is selected, and if c2 <b, C3 is selected. Further, in the above embodiment, only a signal of one frequency is transmitted as a test signal. However, in the fifth embodiment,
A test signal of a plurality of kinds of frequencies is transmitted, and for example, a ratio H / L of a voltage level H of a high frequency wraparound signal and a voltage level L of a low frequency wraparound signal is obtained. It is determined that the amount of attenuation is large. Therefore, in this embodiment, for example, after outputting a 3400 Hz test signal for a predetermined time, a 300 Hz test signal is output for a predetermined time. Further, as shown in FIG. 11, an A / D converter 17 is provided, and a sneak signal is supplied to the A / D converter 17. The control unit 1 first converts the digital value of the voltage level H of the sneak signal of 3400 Hz into A / D converter 17 and stores it in the RAM 18, then obtains the digital value of the voltage level L of the wraparound signal of 300 Hz, calculates H / L, and calculates H / L from the predetermined value. The equalizer may be set or selected as described above depending on whether it is large or small.

[0012]

As described above, according to the present invention,
According to the first aspect of the present invention, the test signal is transmitted to the line side, the frequency characteristic of the wraparound signal of the test signal on which the frequency characteristic of the attenuation in the line is reflected is automatically measured, and the transmission is performed according to the measured frequency characteristic. Since the correction characteristics of the equalizer or the reception equalizer are automatically set, the setting of the correction characteristics of the equalizer does not require labor, and the correction characteristics can be set without depending on the other party's facsimile apparatus. According to the second aspect of the present invention, in the first aspect of the present invention, a test signal having a plurality of types of predetermined frequencies is transmitted, and a frequency characteristic of an attenuation amount in a line corresponding to the plurality of frequencies is reflected. It is measured whether or not the received signal level ratio between the plurality of wraparound signals is equal to or more than a predetermined value (or equal to or less than a predetermined value), and the transmission equalizer or the reception equalizer is determined based on whether the level ratio is equal to or more than a predetermined value (or equal to or less than a predetermined value). Since the ON state or the OFF state is set, the effect of the invention described in claim 1 can be realized, and the realization is easy because only the transmission equalizer or the reception equalizer is set to the ON state or the OFF state. According to a third aspect of the present invention, in the first aspect of the present invention, a test signal having one type of a predetermined (high) frequency is transmitted, and a test signal of a predetermined frequency reflecting a frequency characteristic of an attenuation amount in a line is reflected. It is measured whether the received signal level of the wraparound signal is equal to or less than a predetermined value, and if the signal level is equal to or less than the predetermined value, the transmission equalizer or the reception equalizer is turned on, and if not equal to or less than the predetermined value, the transmission equalizer or the reception equalizer is turned off. Similarly, the effect of the invention described in claim 1 can be realized, and only the transmission equalizer or the reception equalizer is turned on or off, and the frequency of the test signal is only one type, so that the realization is easier. is there. According to the fourth aspect of the present invention, the test signal is transmitted to the line side, the frequency characteristic of the wraparound signal of the test signal reflecting the frequency characteristic of the attenuation in the line is measured, and a plurality of signals are measured in accordance with the measured frequency characteristics. Since the most suitable transmission equalizer or reception equalizer is selected from the transmission equalizer or the reception equalizer, the effect of the invention described in claim 1 can be similarly realized.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of a main part of a facsimile apparatus showing a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a main part of a facsimile apparatus showing a first embodiment of the present invention.

FIG. 3 is an operation flow chart of the facsimile apparatus showing the first embodiment of the present invention.

FIG. 4 is another circuit diagram of a main part of the facsimile apparatus showing the first embodiment of the present invention.

FIG. 5 is an explanatory diagram of a main part of a facsimile apparatus showing a first embodiment of the present invention.

FIG. 6 is an explanatory view of a main part of a facsimile apparatus showing a second embodiment of the present invention.

FIG. 7 is a configuration diagram of a main part of a facsimile apparatus showing a second embodiment of the present invention.

FIG. 8 is a configuration diagram of a main part of a facsimile apparatus showing a third embodiment of the present invention.

FIG. 9 is a configuration diagram of a main part of a facsimile apparatus showing a fourth embodiment of the present invention.

FIG. 10 is a circuit diagram of a main part of a facsimile apparatus showing a fourth embodiment of the present invention.

FIG. 11 is a configuration block diagram of a main part of a facsimile apparatus showing a fifth embodiment of the present invention.

FIG. 12 is an explanatory diagram of a main part of a facsimile apparatus showing an example of the related art.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 control unit, 2 modem, 3 transmission equalizer, 4 reception equalizer, 5 transmission equalizer switching unit, 6 reception equalizer switching unit, 7 2-wire to 4-wire conversion unit, 9
Comparison circuit, 12 amplifier, 13 line transformer, 16
Decoder, 17 A / D converter

Claims (4)

[Claims] 1. A facsimile apparatus having an equalizer for correcting frequency characteristics of a transmission / reception signal, a test signal transmission means for transmitting a test signal to a line side, and a wraparound signal of the test signal transmitted by the test signal transmission means. Frequency characteristic measuring means for receiving and measuring the frequency characteristic thereof, and correction characteristic setting means for setting a correction characteristic of a transmission equalizer or a reception equalizer according to the frequency characteristic measured by the frequency characteristic measuring means. Facsimile machine. 2. The facsimile apparatus according to claim 1, wherein
The test signal transmitting means is configured to transmit a test signal having a plurality of predetermined frequencies, and measures whether or not a received signal level ratio between the plurality of wraparound signals corresponding to the plurality of frequencies is equal to or more than a predetermined value. A facsimile apparatus comprising: a frequency measuring means, and a correction characteristic setting means for setting a transmission equalizer or a reception equalizer to an on state or an off state depending on whether the level ratio is equal to or more than a predetermined value. apparatus. 3. The facsimile apparatus according to claim 1, wherein
The test signal transmitting means is configured to transmit a test signal having one type of predetermined frequency, and the frequency measuring means is configured to measure whether or not the received signal level of the wraparound signal having the predetermined frequency is equal to or lower than a predetermined value. A facsimile apparatus comprising: a correction characteristic setting unit configured to turn on a transmission equalizer or a reception equalizer when the signal level is equal to or lower than a predetermined value, and to turn off the transmission equalizer when the signal level is equal to or lower than the predetermined value. 4. A facsimile apparatus having an equalizer for correcting frequency characteristics of a transmission / reception signal, a plurality of transmission equalizers or reception equalizers having different correction characteristics, test signal transmission means for transmitting a test signal to a line side, Frequency characteristic measuring means for receiving a wraparound signal of the test signal transmitted by the test signal transmitting means and measuring the frequency characteristic thereof; and the plurality of transmission equalizers or reception equalizers according to the frequency characteristic measured by the frequency characteristic measuring means. A facsimile apparatus comprising: an equalizer selecting means for selecting an optimum transmission equalizer or reception equalizer from among them.