JPH02207652A - Dial backup system - Google Patents

Abstract

PURPOSE:To decide the possibility of data transmission before a line is switched to a backup line by transmitting a sine wave near the central frequency of a sound band and a sine wave near the limit frequency of a lower side band from a call originating end, estimating the number of links from the attenuation quantity of a reception level in a call incoming end and comparing the number of the links with the number of data transmittable links. CONSTITUTION:MODEMs 1 and 2 equipped with dial backup function are faced to each other and before backup, modulation/demodulation parts 15 and 16 are connected through a communication line 17. As operation at the time of the backup, the MODEM 1 is connected through a public line 3 and an exchange 4 to the MODEM 2. The sine wave near the central frequency of the sound band and the sine wave near the limit frequency of the lower side band to be transmitted from the call originating end are received in the call incoming end and the levels of the respective sine waves are measured. Then, the number of the links is estimated from this attenuation quantity and compared with the number of the data transmittable links determined in advance. Only when the number is less than a reference value, the backup line is switched. Thus, the possibility of the data transmission can be decided before the line is switched by switch circuits 13 and 14.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dial backup system.

[Conventional technology]

Conventionally, when performing dial backup, backup was performed regardless of the number of links.

[Problem to be solved by the invention]

In the conventional dial backup described above, backup is performed regardless of the number of links, so if the modem's automatic equalizer has a limit or does not have an automatic equalizer, the backup line can be switched. However, there was a problem that data transmission was not possible.

[Means to solve the problem]

The dial backup method of the present invention receives a sine wave near the center frequency of the audio band transmitted from the transmitting end and a sine wave near the limit frequency of the lower band at the receiving end, and measures the level of each sine wave. , estimate the number of links from the attenuation of jin,
The number of links that can transmit data is compared with a predetermined number, and backup line switching is performed only when the number is less than a reference value.

[Effect]

In the present invention, a sine wave near the center frequency of the voice band and a sine wave near the limit frequency of the lower band are transmitted from the transmitting end, the reception level is measured at the receiving end, and the number of links is estimated from this attenuation. , the number of links that can transmit data is compared with a predetermined number of links that can transmit data, and only when the number is less than a reference value, switching to a backup line is performed.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, 1 and 2 are modems (hereinafter referred to as modems) having a dial backup function, and the modems 1 and 2 face each other, and before backup, the modems Is and 1B are connected via the communication line 17. ing. The modem 1 is connected to the modem 2 via the public port 1s3 and the exchange 4 for backup operation.

5 is a sine wave (f,) generator, 6 is a sine wave (f,) generator, 7.8 is a hybrid transformer, 9 is a link estimator,
10 is a switching determination section, 11 is a switching control section, 12 is a level measuring section, and 13 and 14 are switching circuits.

Then, the receiving end receives a sine wave near the center frequency of the audio band and a sine wave near the limit frequency of the lower band transmitted from the transmitting end, measures the level of each sine wave, and links from this attenuation amount. The system is configured to estimate the number of links, compare it with a predetermined number of data-transferable links, and perform backup line switching only if the number is less than a reference value.

FIG. 2 is a diagram showing the spectrum of each of the sine waves (re, Fu) in the audio band used in the present invention.

FIG. 3 is a diagram showing general line frequency characteristics.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

First, a sine wave (
f,) A sine wave (fe) is transmitted from the generating section 5 via the hybrid transformer 7, the modem 2 receives this via the hybrid transformer 8, and the level measuring section 12 measures the reception level. Similarly, a sine wave (!U) generator 6 near the limit frequency of the lower band of the modem 1 transmits a sine wave (fu) via the hybrid transformer 7, and the modem 2
receives this via the hybrid transformer 8, and the level measurement unit 12 measures the reception level.

Next, the difference between the reception levels of each sine wave (Fe) and (Fu) is transmitted from modem 2 to modem 1 using a tone (DTMF), and the link estimator 9 in modem 1 calculates the number of links on public line 3. is estimated and compared with a predetermined number of links that can transmit data in the switching determination section 10, and only when the number is less than the reference value, the switching control section 11 sends a signal to the switching circuit 13 in the modem 1 and the number of links in the modem 2. The switching circuit 14 is controlled to perform dial backup.

Therefore, before connecting the modulation/demodulation sections 15 and 16 via the public line 3 switched by the switching circuits 13 and 14, it is determined whether data transmission is possible, thereby improving backup efficiency.

〔Effect of the invention〕

As explained above, the present invention transmits a sine wave near the center frequency of the audio band and a sine wave near the limit frequency of the lower band from the transmitting end, measures the reception level at the receiving end, and measures the amount of attenuation between the two. By estimating the number of links from , comparing it with a predetermined number of links that can transmit data, and switching to the backup line only if it is less than the standard value, before switching to the backup line. This has the effect of determining whether data transmission is possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 92 is a diagram showing the spectrum of each sine wave used in the present invention, and FIG. 3 is a diagram showing general line frequency characteristics. 1.2...modulation/demodulation equipment, 3...Φ public line, 4.
...exchange machine, 5...φ sine wave (Pc) generator, 6.
...Sine wave (Fu) generation unit, 7.8...Hybrid transformer, 9...Link estimation unit, 10...
, switching determination unit, 11... switching control unit, 12
. . . Level measurement section, 13. 14. . . Switching circuit, 15, 16. Cloud: Modulation/demodulation section, 17. Fist, communication line.

Claims (1)

[Claims] The receiving end receives a sine wave near the center frequency of the voice band and a sine wave near the limit frequency of the lower band transmitted from the transmitting end, measures the level of each sine wave, and calculates the number of links from this attenuation amount. A dial backup method characterized in that the estimated number of links is estimated and compared with a predetermined number of links capable of data transmission, and backup line switching is performed only when the number is less than a reference value.