JPH01192228A - Modulator/demodulator - Google Patents

Abstract

PURPOSE:To set the setting of an equalizing characteristic of an equalizing circuit automatically by allowing a reception equalizing circuit and a transmission equalizing circuit to estimate the amplitude characteristic of a terminal section based on an equalizing characteristic selection signal from a tone of 600Hz and 3000Hz included in the reception signal and setting the equalizing characteristic corresponding to the amplitude characteristic. CONSTITUTION:The modulator/demodulator section 2 of a modulator/ demodurator 20 at the caller detects an AC tone 11 outputs an AC tone detection signal to a control section 1, then the control section 1 outputs a control signal to operate a comparator 7. Moreover, band pass filters 3, 4 always filter a reception signal and output the result to the comparator 7. When the comparator 7 receives the said control signal from the control section 1, the ratio of the output levels with the band pass filters 3, 4 is calculated and an equalizing characteristic selection signal is outputted to a transmission equalizing circuit 5 and a reception equalizing circuit 6. Furthermore, a modulator/demodulator 20 at the called party not receiving the AC tone and a CA tone 12 outputs the equalizing characteristic selection signal to the transmission equalizer 5 and the reception equalizer 6 to switch the automatic equalizing characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is applied to an echo canceller type modulation/demodulation device that transmits data using a telephone line.

In particular, it relates to an equalization circuit that equalizes the amplitude characteristics of a terminal section.

〔overview〕

The present invention provides a modulation/demodulation device that converts the amplitude characteristics of the terminal section into
By estimating from the tone of 000 Hz and setting the equalization characteristic corresponding to this amplitude characteristic, the equalization characteristic of the equalization circuit can be automatically set.

[Conventional technology]

Conventionally, modem equipment that transmits data using telephone lines prepares equalization circuits with two to four different equalization characteristics, measures the amplitude characteristics of the terminal section when setting up the modulation equipment, and calculates the The amplitude characteristics of the line between the modulators and demodulators were equalized by selecting the optimal equalization characteristics for the amplitude characteristics.

FIG. 2 is a diagram showing the equalization characteristics of the equalization circuit of the modulation/demodulation device. In FIG. 2, numerals 8 to 10 indicate equalization curves realized by the equalization circuit. On the other hand, the terminal section is often made up of unloaded cables, and unloaded cables usually have amplitude characteristics that are almost linear when expressed in decibels in the audio band of 0.3 to 3.4 KHz. are doing. Therefore, when installing the modulation/demodulation equipment, the amplitude characteristics of the terminal section are measured, and the measurer determines which of the equalization curves 8 to 10 shown in Figure 2 is optimal, and then sets the equalization characteristics. .

[Problem that the invention seeks to solve]

However, in such conventional modems, the selection and setting of equalization characteristics requires measuring the amplitude characteristics of the terminal section when installing the modem. has to be determined, which makes the equalization characteristic setting work complicated.

The present invention solves the above-mentioned drawbacks, and aims to provide a modulation/demodulation device that can automatically set the equalization characteristics of an equalization circuit.

[Means for solving problems]

The present invention provides a modulation/demodulation device in which the modulation/demodulation section includes means for activating a control section when a tone is detected from the reception equalization circuit, and means for applying the tone to the transmission equalization circuit under the control of the control section; , a first band-pass filter that extracts about 600 frequency components included in a received signal input via a telephone line;
a second band-pass filter that extracts a frequency component of 000 Hz; and equalization characteristic selection according to the amplitude ratio of the output signals of the first band-pass filter and the second band-pass filter under the control of the control section. and a comparator that outputs a signal, and the reception equalization circuit and the transmission equalization circuit further include means for setting an equalization characteristic suitable for the amplitude characteristic of the telephone line based on the equalization characteristic selection signal. It is characterized by including.

[Effect]

When a tone is detected from the reception equalization circuit by the activation means of the modulation/demodulation unit, the control unit is activated to perform control according to the training sequence. The providing means applies the tone to the transmission equalization circuit under the control of this control section and sends it out to the telephone line.

The first band-pass filter extracts the 600 Hz frequency component contained in the received signal input via the telephone line.

Further, a second bandpass filter extracts a frequency component of 3000 Hz included in this received signal. The comparator outputs an equalization characteristic selection signal according to the amplitude ratio of the output signals of the first band-pass filter and the second band-pass filter under the control of the control section. Further, setting means of the reception equalization circuit and the transmission equalization circuit set an equalization characteristic suitable for the amplitude characteristic of the telephone line based on the equalization characteristic selection signal. The above operation allows the equalization characteristics of the equalization circuit to be automatically set.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings. 1st
The figure is a block diagram of a modulation/demodulation device according to an embodiment of the present invention. In FIG. 1, a modulation/demodulation device 20 includes a modulation/demodulation unit 2 including an echo canceller, and a reception signal that has a plurality of types of equalization characteristics and is manually inputted via a telephone line l and a hybrid circuit H to the modulation/demodulation unit 2. An equalization circuit 6, a transmission equalization circuit 5 which has a plurality of types of equalization characteristics and equalizes the transmission signal from the modulation/demodulation section and sends it to the telephone line l via the hybrid circuit H, and controls the training sequence. A control unit 1 is provided.

Here, the features of the present invention are that the modulation/demodulation section 2 includes a means for starting the control section 1 when a tone is detected from the reception equalization circuit 6, and a means for starting the control section 1 when a tone is detected from the reception equalization circuit 6; a first band-pass filter 3 for extracting approximately 600 Hz frequency components contained in the received signal; and a second band-pass filter 3 for extracting approximately 3000 Hz frequency components contained in the received signal. It includes a filter 4 and a comparator 7 that outputs an equalization characteristic selection signal according to the amplitude ratio of the output signals of the bandpass filter 3 and the bandpass filter 4 under the control of the control unit 1, and further includes a reception equalization circuit. 6 and the transmission equalization circuit 5 include means for setting an equalization characteristic suitable for the amplitude characteristic of the telephone line 1 based on the equalization characteristic selection signal.

The operation of the modulation/demodulation device having such a configuration will be explained.

FIG. 3 is a diagram showing received signals during training of the modulator/demodulator of the present invention. FIG. 3 shows the initial part of the handshake sequence described in the CCITT Recommendation.

16 indicates the answer tone, AC)-n 11, CA)-
12 and AC)-13 are all 600Hz+
It is a tone consisting of 3000 seven frequency components, AA)
- tone 14 and CC tone 15 are both 1800 Hz sine waves.

Therefore, the calling side modulation/demodulation device 20 obtains a received signal that has undergone the amplitude characteristics due to the telephone line l, and uses the AC tone 11 and the CA tone 12 to realize automatic equalization characteristic switching of the equalizer. .

This setting procedure will be explained with reference to FIG. When the modem unit 2 detects the AC)-on 11 shown in FIG. 3 in the calling side modem 20 and outputs the AC)-on detection signal to the control unit 1, the control unit 1 operates the comparator 7. Outputs control signals like this.

On the other hand, the band pass filter 3 and the band pass filter 4 are
The received signal is constantly filtered and output to the comparator 7. Therefore, the comparator 7 detects that the received signal from the control unit 1 is AC)-
When it receives a control signal indicating that the band-pass filter 3 and the band-pass-filter 4 are in Output. For example, if the ratio of the output levels of the bandpass filter 3 and the bandpass filter 4 is ΔdB, then the equalization curve 10 as shown in FIG. 2 may be selected. Furthermore, even if the called modem 20 that does not receive the AC tone 11 and the CA tone 12 constantly sets the equalization curve 8 shown in FIG. A transmitting equalizer 5 and a receiving equalizer 6 are installed in the transmitting and receiving sides of the modulation/demodulation section 2, respectively, so as to equalize both of the signals. output, and automatic switching of equalization characteristics can be realized.

〔Effect of the invention〕

As explained above, the present invention can estimate the amplitude characteristics of the terminal section, automatically set the equalization circuit according to the transmission of the echo canceller sequence, and measure the amplitude characteristics between the terminals when installing the modulation/demodulation equipment. This has the excellent effect of omitting the operation of setting the conversion circuit.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a modulation/demodulation device according to an embodiment of the present invention. FIG. 2 is a diagram showing equalization characteristics of an equalization circuit of a modulation/demodulation device. FIG. 3 is a diagram showing received signals during training of the modulation/demodulation device of the present invention. DESCRIPTION OF SYMBOLS 1... Control part, 2... Modulation/demodulation part, 3.4... Band pass filter, 5... Transmission equalization circuit, 6... Reception equalization circuit, 7... Comparator, 8 .9.10...Equalization curve, 11.13...AC)-n, 12...CA)-
tone, 14...AA)-n, 15...CC tone, 1
6...Answer tone, H...Hybrid circuit, l
...Telephone circuit.

Claims (1)

[Scope of Claims] 1. A modulation/demodulation section (2) including an echo canceller, and a reception equalization circuit (6) having a plurality of types of equalization characteristics and supplying the reception signal input via a telephone line to the modulation/demodulation section. , a transmission equalization circuit (5) that has a plurality of types of equalization characteristics and equalizes the transmission signal from the modulation/demodulation section and sends it to the telephone line, and a transmission equalization circuit (5) that controls the modulation/demodulation section according to a training sequence for the echo canceller. In the modulation/demodulation device, the modulation/demodulation unit includes means for activating the control unit when a tone is detected from the reception equalization circuit, and means for transmitting the tone according to the control of the control unit. a first bandpass filter (3) for extracting a frequency component of about 600 Hz included in the received signal; and a means for extracting a frequency component of about 3000 Hz included in the received signal. A second band-pass filter (4) outputs an equalization characteristic selection signal according to the amplitude ratio of the output signals of the first band-pass filter and the second band-pass filter under the control of the control section. a comparator (7), and the reception equalization circuit and the transmission equalization circuit further include:
A modulation/demodulation device comprising means for setting an equalization characteristic suitable for the amplitude characteristic of the telephone line based on the equalization characteristic selection signal.