JPS61192132A - Data transmission system - Google Patents

Abstract

PURPOSE:To attain the quick constitution of the title system, high-quality data transmission and reduction in man-hours by outputting a timing reproducing signal phase-shifted corresponding to delay and distortion of a transmission line based on a code received via either of a code generating circuit generating two kinds of codes and sending them to a transmission circuit or an equalizer and connecting the signal switching to an optimum equalizer. CONSTITUTION:A code generating circuit 9 at the transmission station T generates prescribed two kinds of codes (mark M1 and space M2) and sends them to a voice line 3. A reception station R outputs a timing recovery signal A giving phase shift corresponding to a delay distortion to a voice line 3 according to the codes M1, M2 received through a selector 5 to select the optimum equalizer, reproduces a reception data Dm by using a demodulation timing from a timing recovery circuit 7 and sends the result to a terminal device 8 as data D.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data transmission system that performs data transmission using a voice line.

BACKGROUND TECHNOLOGY Generally, data transmission using a voice line is subject to deterioration due to the delay distortion characteristics of the line. Therefore, data transmission equipment usually includes a delay equalization circuit for the purpose of preventing deterioration, and in particular automatic equalization In a data transmission device that does not have a delay equalizer, it is essential to provide a delay equalizer.

FIG. 3 is a block diagram showing an example of a conventional data transmission system of this type. As shown in FIG. 3, the transmission data D is calculated 41! The signal is sent from l a to the transmitting circuit 2 , which modulates it (as Dll) and transmits it to the partner station via the audio line 3 .

The signal 1 received at the other station is multiplied by passing through the most suitable equalizer for equalizing line distortion among the equalizers 4-+ to 4-n, which are artificially selected by the selector 5. The signal is sent to circuit 6 and timing recovery circuit 7a. Based on this signal 1, the timing reproducing circuit 7a creates the timing necessary for demodulation, and the receiving circuit 6 regenerates the received data using the timing, and sends it as data D to the terminal device 8 for data transmission.

[Problem that the invention seeks to solve]

In the conventional data transmission system described above, when selecting an appropriate equalizer, service personnel etc. measure the distortion of the audio line.
It is necessary to manually select the optimal equalizer based on the measurement results, which has the disadvantage of requiring a lot of effort to start up the online system. In addition, when using a switched line, it is necessary to dial in order to transmit data, and the line characteristics change each time a connection is made to the other party, making it impossible to select the optimal equalizer and There was a drawback that the transmission had to be carried out in a degraded state.

An object of the present invention is to provide a data transmission system that automatically sets the optimum equalizer for a line among a plurality of equalizers, eliminates complicated labor, and enables data transmission in good conditions. There is a particular thing.

[Means for solving problems]

Generally, the delay distortion characteristic of an audio line is flat in the center of the band, and the distortion increases as it approaches the edge of the band. This effect degrades the data transmission characteristics, but the effect is, for example, CCITT V,2[i or V,28
This is especially noticeable when regenerating the reception timing of a data transmission device that complies with the BIS recommendations. In other words, the reception timing essential for reproducing the received data in the receiving section is reproduced from the signal sent from the transmitting section via the audio line, but due to delay distortion caused by the audio line, the phase of the reproduced timing waveform cannot be specified. The data transmission quality may shift in the direction of deterioration for the data transmission code. This amount of deviation is proportional to the amount of delay distortion, so by measuring this amount of phase deviation, it is possible to estimate the amount of delay distortion, that is, the amount of delay equalization required, and this determines the equalizer that should be selected. This means that you can make a choice.

The present invention utilizes such a principle, and includes a transmitting circuit that modulates data and sends it to a transmission path, and a plurality of parallel-connected transmitting circuits that receive the modulated data and have different characteristics. an equalizer, a selector that artificially selects one of these equalizers, and a receiving circuit that demodulates the above-mentioned modulated data input through the equalizer selected by the selector. In a data transmission system equipped with the above-mentioned code, a code generation circuit generates two types of codes prior to the above-mentioned data and sends them to the transmission circuit, and a code generation circuit that generates two types of codes prior to the above-mentioned data and sends the above-mentioned codes to the above-mentioned code received via one of the above-mentioned equalizers. Based on this, a timing regeneration circuit that outputs a timing regeneration signal whose phase shifts in accordance with the amount of delay distortion in the transmission path, and an optimal equalizer among the above-mentioned equalizers for the above-mentioned selector based on this timing regeneration signal. It is characterized by having a timing movement amount detection circuit that sends out a selection command signal to be switched and connected to the equalizer.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a data transmission system according to the present invention. Audio episode between transmitting station T and receiving station R!
Connected via i3.

On the transmitting station T side, a computer 1 that outputs data D and a computer 4111 are provided therein. A code generation circuit 9 outputs two predetermined types of codes (mark M+ and space M2) before data D, and a code M! and M2 to the voice line 3, and a transmitting circuit 2 which changes the data D to JJR (denoted as DII) and sends it to the voice line 3.

On the other hand, the receiving station R side has a plurality of equalizers 4-1 to 4-n connected in parallel to which codes Ml and M2 and data islands sent via the audio line 3 are input, and a timing shift amount. A selector 5 that selects the optimal one of the equalizers 4-r to 4-n in response to a selection command signal B from a detection circuit 10 (described later), and a selector 5 that selects the optimal one of the equalizers 4-r to 4-n; The code M received through the selector 5
1 and M2, audio times i! A timing regeneration circuit 7 outputs a timing regeneration signal A whose phase is shifted in accordance with the delay distortion amount of No. 3 and sends it to the timing movement amount detection circuit IO, and a selection command signal B based on the timing regeneration signal A.
After selecting the timing movement amount detection circuit lO that outputs the data D
a receiving circuit 6 that sends the signal to the terminal device M8, and a terminal device 8.
It is composed of.

FIG. 2 is a diagram showing an example of the configuration of the timing movement amount detection circuit 10. As shown in FIG. Generally, the timing recovery circuit 7 converts the timing components extracted from the received codes M+ and M2 into
A PLL system is adopted to synchronize its own clock system, and in this case, phase advance control and phase delay control are normally performed as control of its own clock.

Assume now that equalizer 4-1 is selected.

The timing recovery circuit 7 includes the audio line 39 equalizer 4-11.
When the code city and M2 are received through the selector 5, as described above, a timing reproduction signal A whose phase is shifted corresponding to the amount of delay distortion of the audio line 3 is generated, and it is used as a pulse advance control signal A and a pulse phase advance control signal A. The combination of the delayed phase control signal A2 is sent to the timing movement amount detection circuit 10.

The timing movement amount detection circuit 10 receives a phase advance control signal AI.
(or when the slow phase control signal ^2) is input.

Switch S+ (or switch S2) is closed, and capacitor C is charged by power supply [10V] (or power supply [-Vl). Therefore, the output terminal voltage, in other words, the selection command signal B becomes a different analog voltage depending on the combination of the respective pulses of the input control signals ^1 and A2. This analog voltage indicates the timing phase at each time, and based on the magnitude, the selector 5
is switched and connected to the optimum equalizer among the equalizers 4-1 to 4-n.

〔Effect of the invention〕

As explained above, the present invention automatically sets the optimal equalizer, so it is possible to measure line characteristics and set the equalizer, which conventionally required a large amount of human labor, and which was previously impossible. This makes it possible to set the equalizer optimally on switched lines, which has the effect of contributing to rapid system construction, high-quality data transmission, and a reduction in human labor.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a data transmission system according to the present invention, 2 Ugi is a diagram showing an example of the configuration of the timing movement amount detection circuit 10, and FIG. 3 is a block diagram showing an example of a conventional data transmission system. It is a diagram. 1... Computer, 2... Transmission circuit. 3...Audio line, 4-1 to 4-n...Equalizer. 5... Selector, 6... Receiving circuit. 7... Timing regeneration circuit, 8... Terminal device. 9... Code generation circuit. 10... Timing movement amount detection circuit. A (A+, A2)...Timing reproduction signal. B...Selection command signal, D (Dll)...Data. f'l, M2... code, T... transmitting station. R...Receiving station.

Claims (1)

[Claims] A transmission circuit that modulates data and sends it out to a transmission path, a plurality of parallel-connected equalizers with different characteristics to which the modulated data is input, and one of the equalizers that is artificially In a data transmission system, the data transmission system includes a selector that selects an equalizer, and a receiving circuit that demodulates the modulated data input through the equalizer selected by the selector,
A code generation circuit that generates two types of codes prior to the data and sends them to the transmission circuit, and the amount of delay distortion of the transmission path based on the code received via either of the equalizer. a timing regeneration circuit that outputs a timing regeneration signal whose phase is shifted in accordance with the timing regeneration signal; and a selection command signal that causes the selector to switch and connect to an optimal equalizer among the equalizers based on the timing regeneration signal. A data transmission system comprising: a timing movement amount detection circuit for transmitting a timing movement amount detection circuit.