JPH07115478A - Network control unit - Google Patents

Abstract

PURPOSE:To obtain a network control unit for full duplex communication capable of attaining miniaturization and thinning and provided with a hybrid function. CONSTITUTION:A transmission signal from terminal equipment is inputted to a transmission light coupling part 2 consisting of a photocoupler and a waveform adjusting part 12 via a transmission amplifier 1. The transmission signal is sent to a telephone line via the transmission light coupling part, and is transmitted to an opponent. Simultaneously, the transmission signal sneaks via a reception light coupling part 8, and it is inputted to a reception side amplifier 9, then, it becomes the cause of a noise. However, the output of the waveform adjusting part is also inputted to the reception amplifier differentially, and since the output of the waveform adjusting part is adjusted in shape almost equal to that of a sneaking transmission signal by distorting or changing the phase of the transmission signal, both signals can be canceled. Therefore, only a reception signal sent via the telephone line is transmitted to a reception means in the terminal equipment via the reception light coupling part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a network control device for connecting a terminal device or the like to a telephone line network.

[0002]

2. Description of the Related Art In a network interface of a network control unit (NCU), it is necessary to perform direct current insulation and to combine alternating current signals to be transmitted. Further, in the case of full-duplex communication using a normal telephone line, it is necessary to have a hybrid function that prevents the transmission signal from the local station from returning as a reception signal. Therefore, the various functions are usually realized by mounting a component called a hybrid transformer in the circuit.

[0003]

However, the transformer is inevitably limited in size reduction due to its structure, has a problem that it is heavy and difficult to be thinned. As a result, modems (especially card-type modems),
It is not suitable for being incorporated in a small size and light weight in a facsimile or the like, and it is one of the necks for thinning such products.

In order to reduce the size of the transformer, there is a transformer in which a capacitor is used instead of the transformer so that only an AC component can pass through. However, since the capacitor alone cannot obtain a sufficient withstand voltage, a separate protection circuit is required. It requires a complicated circuit.

Further, a system using an optical coupling element such as a photo coupler has been attempted for transmission only, reception only, or half-duplex communication. However, if it is applied to full-duplex communication as it is, since the optical coupling element has directionality, one optical coupling element is mounted in each of the transmitting section and the receiving section, and since the telephone line side has two lines, The line-side end of the optical coupling element is connected.

Then, the signal sent from the transmitting unit in the terminal device is sent to the telephone line through the transmitting side optical coupling element,
Due to the directivity, the reception signal sent from the telephone line side does not pass through the transmission side optical coupling element but passes through the reception side optical coupling element and reaches the receiving section in the terminal device. Here, focusing on the signal that has passed through the transmitting side optical coupling element, since such a signal is transmitted to the telephone line side as described above and also exists at the input side of the receiving side optical coupling element at the same time, It is transmitted to the receiving section through the coupling element (a wraparound signal is generated). That is, the hybrid function, which is one of the functions that the network control device should have, is not satisfied.

By the way, since the transmission signal and the reception signal are used in different frequency bands as shown in FIG. 4, a predetermined band pass filter is installed to remove the above-mentioned sneak signal and only the normal reception signal is obtained. Can pass through. However, in the case of such a wraparound signal, the transmitting side,
Since it passes through the two optical coupling elements on the receiving side, the signal waveform is distorted and the phase is shifted each time, so that it does not look similar to the waveform of the transmitting signal, and the other side (receiving side) There is a possibility that it will fall into the frequency band used by the above, and in such a case, the signal cannot be separated by the filter.

The present invention has been made in view of the above background. An object of the present invention is to reduce the size and thickness of a network control device by using an optical coupling element as a line interface. Moreover, it is to provide a network control device having a hybrid function even in full-duplex communication.

[0009]

In order to achieve the above-mentioned object, a network control device according to the present invention is arranged between a telephone line and a terminal device and controls the connection between the two. In, rectifying means for rectifying a signal on the telephone line, transmitting side optical coupling means for receiving a transmission signal from the terminal device and capable of transmitting the transmission signal to the telephone line in an electrically insulated state, Receiving output signal from the telephone line, receiving side optical coupling means for outputting the receiving signal in an electrically insulated state, and transmitting signal before input to the transmitting side optical coupling means, to the transmission signal On the other hand, the waveform adjusting means for performing a predetermined waveform adjustment such as distorting the waveform and changing the phase, the output of the waveform adjusting means, and the output of the receiving side optical coupling means are received in the differential coupling state and Amplify the It was composed of a differential amplifier means for enabling transmission to the receiving means in the apparatus.

[0010]

The transmission signal is transmitted to the telephone line through the transmission side optical coupling means and the rectification means, and is circulated through the reception optical coupling means and input to the differential amplification means. The transmission signal is input to the differential amplification means after being distorted by the waveform adjusting means or having its phase changed. The differential amplifying means differentiates the adjusted signal and the loop-in signal, so that both signals are canceled. Therefore, almost no signal (noise) accompanying the sneak is output to the output of the differential amplifying means. Further, when the received signals are simultaneously input at this time, the waveform-adjusted signal cancels the sneak signal and does not affect the received signal. Therefore, only the received signal is input to the receiving unit of the terminal device. Thereby, the hybrid function is achieved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a network control device according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a diagram showing a block configuration of a first embodiment of the present invention, and FIG. 2 shows a concrete circuit example thereof. As shown in the figure, the input terminal of the transmission amplifier 1 is connected to a modem LSI (not shown), and the modem L
The transmission signal (modulation signal) sent from SI is amplified and then input to the transmission optical coupling unit 2. Then, in practice, the transmission amplifier 1 amplifies and outputs a signal in a desired frequency band through a predetermined filter so as to satisfy the unnecessary transmission power regulation.

The transmission light coupling section 2 uses a photocoupler having a light emitting diode 2a and a phototransistor 2b as shown in the figure. The light emitting diode 2a is stably supplied with a constant DC bias current from the bias supply section 3. It is like this.

The output (phototransistor 2b) of the transmission light coupling section 2 is connected to the telephone line from the pseudo inductance circuit 4 via the rectification section 5, and the amplified transmission signal is transmitted to the communication partner via the telephone line. Will be transmitted.
It should be noted that the pseudo-inductance circuit 4 is used to set the current value flowing through the DC closed circuit to a predetermined value.
As shown in FIG. 3, it is configured by connecting two transistors in Darlington connection. Further, the rectifying unit 5 uses a general one in which diodes are bridge-connected.

On the other hand, the received signal sent from the telephone line is inputted to the light emitting diode 8a which is the input section of the received light coupling section 8 via the rectifying section 5 and the pseudo inductance circuit 4. Then, the photodiode 8b, which constitutes the receiving optical coupling section 8 together with the light emitting diode 8a, receives the above-mentioned received signal, and the received signal is inputted to the receiving side amplifier 9 where it is amplified and then a modem not shown in the figure. It will be input to the LSI. The light emitting diode 8a is also supplied with power from the bias supply unit 10 and operates stably. As shown in FIG. 2, the bias supply unit 10 has a basic configuration in which a predetermined voltage is applied to the Zener diode.

In the present invention, the receiving side amplifier 9 is a differential amplifier, the output of the receiving optical coupling section 8 is connected to one output terminal, and the output of the transmitting side amplifier 1 is connected to the waveform adjusting section 12. It is connected to the other input terminal of the differential amplifier via. As a result, when the transmission signal is being output, the transmission signal
(A signal before being input to the receiver), a signal having a predetermined waveform adjustment is input to the reception side amplifier 9, and a difference between the signal and the reception signal sent through the reception optical coupling unit 8 is taken. A signal obtained by amplifying the difference signal becomes a reception signal input to the modem LSI.

The waveform adjusting section 12 distorts, delays or advances the phase of a given signal (transmission signal), and further increases or decreases its amplitude. Output is adjusted so as to be a waveform signal substantially equal to the signal sneak through via the transmission light coupling section 2 and the reception light coupling section 8.

As a result, the transmission signal is transmitted by the transmission light coupling section 2, the pseudo inductance circuit 4, and the rectifier 5 as described above.
At the same time as being transmitted through the receiving optical coupling section 8, it is input to the light emitting diode 8a of the receiving optical coupling section 8, shunts through the receiving optical coupling section 8, and is input to the non-inverting input terminal of the receiving side amplifier 9. At this time, At the inverting input terminal of the receiver amplifier 9,
Since the waveform-adjusted signal (having substantially the same shape as the loop-in signal) is input, both signals are canceled. Therefore, the output of the reception-side amplifier 9 outputs almost no signal accompanying the sneak, and the hybrid function is achieved.

Further, if the received signals are simultaneously input at this time, the waveform-adjusted signal only cancels the sneak signal and does not affect the received signal. further,
In the case of only the reception signal (there is no transmission signal), the output of the waveform adjusting unit 12 becomes zero and the input signal to the inverting input terminal of the reception side amplifier 9 becomes zero, so that the reception signal has a predetermined amplification factor. After being amplified, it is input to the modem LSI.

As a concrete circuit configuration of the waveform adjusting section 12, in this example, as shown in FIG. 2, a resistor R and a variable resistor R'are connected in series to form a basic configuration. When the resistance value of the variable resistor R ′ is changed, the voltage division ratio is changed, and the output capacitance of the transmission side amplifier 1, the parasitic capacitance of each element, the correlation with the input capacitance of the reception side amplifier 9 influences the phase, etc. Also fluctuates. As a result, desired (cancel) waveform adjustment can be performed. In the illustrated example, since the configuration is simple, it is difficult to completely match them. However, in such a case, it is preferable that at least the frequency band of the signal that remains unremoved deviates from the band of the received signal. (Because it can be removed by the subsequent filter).

FIG. 3 shows the essential parts of the second embodiment of the present invention. In this example, as the waveform adjusting unit 12 ', the above-mentioned transmission,
A basic structure is obtained by multi-stage coupling two photocouplers 14 and 14 having the same characteristics as the reception light coupling units 2 and 8, and a portion indicated by reference numeral A in FIG. 2, that is, the transmission side amplifier 2 and the reception side amplifier 8 is provided. Implemented in between.

With this configuration, the transmission signal is
The same distortions, time delays, and the like caused by passing through the transmitting / receiving optical coupling units 2 and 8 can be obtained by passing through the two dummy photocouplers 14 and 14.
It is possible to obtain an adjusted waveform signal that is closer to the actual wraparound signal. As a result, a higher hybrid function can be achieved. Furthermore, further fine adjustment can be performed by changing the capacitor connecting both photocouplers 14, 14 and the resistance value.

In the present embodiment, the configuration of the adjusting unit composed of the resistors R and R'as shown in FIG. 2 may be left for fine adjustment, or may be omitted (the waveform adjusting unit is not provided). Figure 3
The configuration shown in) is good.

[0023]

As described above, in the network control apparatus according to the present invention, the transmission signal is sent together with the transmission optical coupling means to the waveform adjusting section, and after being transformed into a desired waveform shape, the differential amplifying means (reception on the receiving side). Since the signal is input), it is possible to cancel the signal which the transmission signal has sneak through via the receiving side optical coupling means. Moreover, since the rotation signal is not simply compared with the transmission signal to be canceled but the waveform is adjusted, even if the signal is distorted by passing through the optical coupling means, it can be reliably canceled. Therefore, the hybrid function can be exhibited even in full-duplex communication. As a result, the line interface can be performed using the optical coupling element, and the size and thickness can be reduced.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a specific circuit configuration of the first embodiment.

FIG. 3 is a diagram showing a main part of a second embodiment of the network control device according to the present invention.

FIG. 4 is a diagram illustrating a used frequency band.

[Explanation of symbols]

 1 Transmitter-side amplifier 2 Transmitter-optical coupler 5 Rectifier 8 Received-optical coupler 9 Receiver-side amplifier

Claims (2)

[Claims] 1. Arranged between a telephone line and a terminal device,
In a network control device for controlling the connection between the two, rectifying means for rectifying a signal on the telephone line, and a transmission signal from the terminal device, and the transmission signal to the telephone line in an electrically insulated state. Transmitting side optical coupling means capable of transmission, receiving side optical coupling means for receiving a reception output signal from the telephone line and outputting the reception signal in an electrically insulated state, and input to the transmission side optical coupling means Waveform adjusting means for receiving the previous transmission signal and performing predetermined waveform adjustment such as distorting the waveform and changing the phase with respect to the transmission signal, the output of the waveform adjusting means, and the output of the receiving side optical coupling means And a differential amplifying means capable of performing predetermined amplification and transmitting the same to a receiving means in the terminal device. 2. The waveform adjusting means comprises at least a plurality of optical coupling means having substantially the same characteristics as those of the transmitting side optical coupling means and the receiving side optical coupling means, which are connected in multiple stages. 1. The network control device described in 1.