JPH0326161A - Modem - Google Patents

Abstract

PURPOSE:To automatically adjust the transmitting levels of a selfstation and other stations by providing a receiving level comparing circuit to compare the receiving level of the selfstation with a normal value, an adjusted sound output circuit to output an adjusted sound different in frequency with the comparison result, an adjusted sound detecting circuit to detect the adjusted sound sent from the other station and a transmission amplifying circuit to increase and decrease the transmitting level of the self-station with the detection result. CONSTITUTION:When a line is connected, the self-station outputs the adjusted sound of fG and waits for the adjusted sound from the other station. When the adjusted sound of fG, fH or fL from the other station is received, the receiving level is detected by a receiving level comparing circuit 3, and a signal is sent to an adjusted sound output circuit 8 so as to output the adjusted sound of fH when the receiving level is higher than a normalized range, the adjusted sound of fL when the receiving level is lower than the normalized range and the adjusted sound of fG when the receiving level is within the normalized range. When the frequency of the adjusted sound detected by an adjusted sound detecting circuit 5 is at fH, the amplification ratio of a transmission amplifying circuit 9 is made small, the transmitting level of the self-station is gradually lowered, and when the adjusted sound is at fL, the amplification ratio of the transmission amplifying circuit 9 is made high and the transmitting level of the self-station is gradually raised.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a modulation/demodulation device used for data communication using an analog communication network such as a telephone line, and in particular to a modulation/demodulation device used for an unspecified number of general users. The present invention relates to modulation/demodulation equipment that is installed in a place where sufficient maintenance is difficult, and is operated in a public switched circuit network, etc., where the line connection destination and connection route are undefined.

[Conventional technology]

Conventionally, this type of modulation/demodulation equipment has a variable resistor to adjust the transmission level, because if the reception level is not within the appropriate range, errors will occur in the received data and communication will be difficult. The reception level of the equipment was adjusted to be within the specified range. [Problems to be Solved by the Invention] The conventional modulation/demodulation device described above measures the receiving level of its own station with a measuring device in order to make the receiving level of its own station appropriate.
The transmission level of other stations will be adjusted. Similarly, in order to make the reception level of the other station appropriate, the reception level of the other station is measured with a measuring device, and the transmission level of the own station is adjusted. To perform this work, multiple workers must travel to remote locations where the modem is installed, measure their respective reception levels, and communicate information with each other to adjust the transmission level of the other party. This has the disadvantage that adjustment work requires a lot of manpower and takes a long time. At this time, even if the modem is properly adjusted, there is a drawback that readjustment is required if the reception level exceeds a specified range due to changes in temperature or aging of circuit components. In addition, even if the modem is properly adjusted between two points in this way, when using a public switched network such as a telephone line, the reception of the own station may change depending on the connection or the other party. The level fluctuates.
When communicating with unspecified parties using a public switched network, there is also the drawback that it becomes difficult to maintain the reception level within a specified range.

[Means to solve the problem]

The modem of the present invention is a modem that is used for data communication using an analog communication network, and includes a reception level comparison circuit that compares the reception level of its own station with a specified value, and a comparison between the reception level comparison circuit and the reception level comparison circuit. There is an adjustment sound output circuit that outputs adjustment sounds with different frequencies depending on the result, an adjustment sound detection circuit that detects the frequency of the adjustment sound sent from other stations, and a transmission level of the own station based on the detection result of this adjustment sound detection circuit. It is configured to include a transmission amplifier circuit that increases and decreases.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

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

A control circuit 2 controls each part in the modulation/demodulation device l. The reception amplifier circuit 4 amplifies the signal input from the line to a constant level, and the demodulation circuit 6 converts the output of the reception amplifier circuit 4, which is an analog signal, into a digital signal and outputs it to the CPU. The modulation circuit 7 converts the digital signal input from the CPU into an analog signal, which is further amplified by the transmission amplifier circuit 9 and output to the line.

The above is the same as the conventional modulation/demodulation device.

The reception level comparison circuit 3 compares the reception level of the signal input from the line with the prescribed reception level, and the adjustment sound output circuit 8 outputs an adjustment sound based on the output of the reception level comparison circuit 3. The adjustment sound is fa. Either one of fn or fz (Hz) frequencies is output. The adjustment sound detection circuit 5 detects whether the adjustment sound received from the line has a frequency fo, fw or fL (Hz). The transmission amplifier circuit 9 can change the amplification ratio according to the output of the adjustment sound detection circuit 5. The reception level specification values include an upper limit specification value and a lower limit specification value. The reception level comparison circuit 3 outputs an adjustment sound of fm (Hz) if the reception level is higher than the upper limit value, and outputs an adjustment sound of fL (Hz) if the reception level is lower than the lower limit value. If it is between the upper and lower specified values,
The adjustment sound output circuit 8 can be requested to output the adjustment sound of z). The upper limit specified value and the lower limit specified value are stored in a device that is determined within the appropriate reception level range.

When the modulation/demodulation apparatus of this embodiment is used for the own station and other stations to which it is connected, the operation is as follows. When the line is connected, the own station becomes f. Outputs the adjustment sound and waits for the adjustment sound from other stations. fa, fm or ft. from another station. When the adjustment sound of is received, the reception level is detected by the reception level comparison circuit 3, and if the reception level is higher than the specified range, the adjustment sound of f1I is adjusted, and if the reception level is lower than the specified range, the adjustment sound of fL is adjusted. f when the reception level of the sound is within the specified range.

A signal is sent to the adjustment sound output circuit 8 to output the adjustment sound. The output of the adjusted sound output circuit 8 is amplified by a transmission amplifier circuit 9 and sent to another station.

Further, the frequency of the adjustment sound detected by the adjustment sound detection circuit 5 is f
When the signal is ft.vc, the amplification ratio of the transmission amplifier circuit 9 is made small, the transmission level of the own station is gradually lowered, and the adjusted sound is adjusted to ft. In this case, the amplification ratio of the transmission amplifier circuit 9 is increased to gradually raise the transmission level of the own station.

This adjustment operation is similarly executed on the other stations.

The operation of this embodiment will be explained using FIG. At first, my own station is f. The adjustment sound 21 is output. When an adjustment sound 22 arrives from another station, if the receiving level of the own station is higher than a specified range, an f-yo adjustment sound 23 is output. The other station gradually lowers the transmission level while receiving the f8 adjustment tone. Therefore, the reception level of your own station gradually decreases (adjustment sound 24
), falling within the defined range (reference number 25). Here, the own station outputs the adjustment sound 26 of f0 to inform the other stations that the adjustment has been completed. The other station receiving the adjustment sound 26 of fo fixes the transmission level to the amplification ratio at that time (adjustment sound 27).

Own station f. If the output of the adjustment sound and the input of the adjustment sound of f0 from the other station continue for a certain period of time, the adjustment ends normally. Next, like conventional modulation/demodulation equipment, the own station transmits a carrier wave, and data communication becomes possible when the station receives a carrier wave from another station. When the adjustment sound f0 cannot be output from the own station within a certain period of time,
Alternatively, if the adjustment sound f0 cannot be input from another station, the line connection will fail and be disconnected. Also, if it is presumed that the other station is a modem that does not respond to this adjustment tone,
Attempt to connect by omitting this adjustment step.

〔Effect of the invention〕

As explained above, the present invention includes a reception level comparison circuit that compares the reception level of its own station with a specified value, an adjustment sound output circuit that outputs adjustment sounds with different frequencies depending on the comparison result,
an adjustment sound detection circuit that detects adjustment sounds sent from other stations;
By having a transmission amplifier circuit that increases or decreases the transmission level of the local station based on the detection result, the transmission level of the local station and other stations can be automatically adjusted, and the receiving level of each station can be adjusted appropriately.

In addition, when installing a new device, there is no need for manual adjustment, which reduces the cost of installation, and automatic adjustment is performed each time a line is connected, making it possible to use the public switched network for unspecified applications. This has the effect of maintaining an appropriate reception level when communicating with the station, and reduces operational costs by eliminating the need for manual readjustment even when the temperature changes or changes over time.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention. FIG. 2 is a time chart showing the operation of the embodiment shown in FIG. 1... Modulation/demodulation device, 2... Control circuit,
3...Reception level comparison circuit, 4...Reception amplification circuit, 5...Adjustment sound detection circuit, 6...
... Demodulation circuit, 7 ... Modulation circuit, 8 ...
... Adjustment sound output circuit, 9... Transmission amplification circuit.

Claims (1)

[Claims] In a modulation/demodulation device used for data communication using an analog communication network, there is a reception level comparison circuit that compares the reception level of the own station with a specified value, and an adjustment sound with a different frequency based on the comparison result of this reception level comparison circuit. an adjustment sound output circuit that outputs the adjustment sound, an adjustment sound detection circuit that detects the frequency of the adjustment sound sent from another station, and a transmission amplification circuit that increases or decreases the transmission level of the own station based on the detection result of the adjustment sound detection circuit. A modulation/demodulation device comprising: