JPH037460A - Signal transmission level setting device - Google Patents

Abstract

PURPOSE:To prevent a reception error by keeping a reception level at a signal receiving end at a reference level or below at all time. CONSTITUTION:The device consists of a level adjustment means 2 converting a modulation signal into a prescribed level and sending the result to a signal transmission line and a level designation means 6 designating a signal transmission level to set a reception level of an opposite device to a reference level or below to the level adjustment means 2 in response to a detection output of a level detection means 4. Thus, the level of a sending end of the signal transmission line is detected to detect a level in response to the transmission loss of the signal transmission line and it is possible to set the reception level to the reference level or below at all time by selecting a level matching the detected level to the reference level or below. Thus, the reception error is prevented.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a signal transmission level setting device that uses dial tone, etc. from a modem to set the transmission level when setting up a line, and automatically sets the signal transmission level below a reference level at the time of line formation. In a communication terminal device that sends a modulated signal to a line formed by sending a signal to form a line with a partner device, the level of the modulated signal is converted to a predetermined level and the signal is converted to a predetermined level. level adjusting means for sending signals to a transmission line; level detecting means for detecting a sending end level of a signal for forming said line; and a level detecting means for detecting a receiving level of said partner device in response to a detection output of said level detecting means. The present invention includes level specifying means for specifying, to the level adjusting means, a signal sending level to be set below the reference level.

[Industrial application field]

The present invention relates to a signal transmission level setting device, and more particularly to a signal transmission level setting device that uses a dial tone or the like from a modem to set the transmission level when setting up a line.

[Prior Art] When transmitting a signal from a modem installed on a telephone line to a terminal station, when a call is made to the other party, the dial tone generator 16 generates an analog dial signal as shown in FIG. When the modulated signal is sent to the telephone line 12 via the switch 18 and the line transformer 34 and a line is formed with the other party, the modulated signal is sent to the level attenuator 32 and the analog switch 1.
8. The signal is sent to the telephone line 12 via the line transformer 24. At this time, the level of the signal sent from the modem 10 to the telephone line 12 is determined so that the reception level at the terminal station 14 is 115 dBn+ or less. Therefore, when the modem 10 is installed on the telephone line 12, the output level of the level attenuator 32 is manually adjusted so that the receiving level at the terminal station 14 is -15 dBm or less. .

[Problem to be solved by the invention]

However, since the transmission loss of the telephone line connected to the modem 10 is not constant, even if the level is adjusted by the level attenuator 32, the output level of the modem may not be adjusted to the optimum level. That is, even if the adjustment level of the level attenuator 32 is uniquely determined, if the transmission loss of the telephone line is not constant, it may not be possible to set the modem's output level to the optimum level. Therefore, the reception level becomes insufficient, and a reception error may be mixed into the reception of the reception signal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a signal transmission level setting device that can automatically set a signal transmission level below a reference level at the time of line formation.

[Means for Solving the Problems] FIG. 1 shows a block diagram of the principle of the present invention. As shown in this figure, the present invention provides a communication terminal device that sends a modulated signal to a line formed by sending a signal for forming a line with a partner device, in which the level of the modulated signal is set to a predetermined level. a level adjusting means 2 for converting the signal into a signal and sending it out to the signal transmission line; a level detecting means 4 for detecting the sending end level of the signal for forming the line; The device includes a level specifying means 6 for specifying, to the level adjusting means, a signal sending level for setting the reception level of the partner device below a reference level.

In the figure, reference numeral 8 denotes a switch that is switched to transmit a modulated signal after transmitting a dial tone or the like.

[For production]

By detecting the level at the sending end of the signal transmission line, it is possible to detect the level corresponding to the transmission loss of the signal transmission line, and by selecting a level that matches the detection level below the reference level, the reception level can be constantly maintained. It becomes possible to set it below the standard level.

〔Example〕

In FIG. 2, a modem 10 is connected to a terminal station 14 via a telephone line 12, and the modem IO includes a dial tone generator 16, an analog switch 18, a sending level adjuster 20, a detection circuit 22, and a line transformer 24. is provided.

Dial tone generator 16 is configured to send two signals of different frequencies to analog switch 1. The sending level adjuster 20 is configured as a level adjusting means that converts the level of the input signal to a specified level and sends it to the analog switch 18, and has 16 resistors to adjust the level of the input signal in 16 steps. The resistor is provided with a switch circuit for selecting a designated resistor based on signals from the resistor and the detection circuit 22. The analog switch 18 is connected to the dial tone generator 16 or the output level adjuster 20.
The selected signal is sent to the line transformer 24 via the signal line 26.

The detection circuit 22 includes an A/D converter and a digital signal processor 30, takes in the signal on the sending end side of the signal line 26 when sending out a dial tone for line formation, and converts the signal to that level. The level of the converted digital signal is compared with the setting level for setting the reception level below the reference level, and the level for suppressing the deviation between the two to zero is calculated. A level designation signal corresponding to the value is sent to the sending level adjuster 20. When selecting this level designation signal, a 4-bit signal is used, and the telephone line 12
It is possible to specify 16 levels of signal transmission depending on the transmission loss.

That is, the detection circuit 22 constitutes a level detecting means and a level specifying means.

In the above configuration, when a dial signal is output from the dial tone generator 16 when making a call, this signal is transmitted to the analog switch 18, the signal line 26, and the line transformer 2.
4. Transmitted to the terminal station 14 via the telephone line 12.

At this time, the signal level of the signal line 26 is at a level corresponding to the transmission loss of the telephone line 22 (see Figure 6).
, the signal level is detected by the detection circuit 22, and calculation is performed to select the signal output level from the modem IO according to the transmission loss of the telephone line 12. That is, the reception level of the terminal station 14 is set to its reference level, for example -15 dB.
A calculation is performed to select the signal sending level to make the signal m.

Then, a resistor in the output level adjuster 20 is selected according to the selected level, and processing is performed to set the level of the modulated signal at the terminal station 14 to -15 dBm.

In this way, when a line is formed between the modem 10 and the other party that supports dialing signals via the terminal station 14, the analog switch 18 is switched, and the modulated signal is sent to the output level adjuster 20, analog switch 18, The signal is transmitted to the terminal station 14 via the signal line 26, line transformer 24, and telephone line 12, and used for communication.

In this way, in this embodiment, the output level of the output level adjuster 20 can be automatically adjusted according to the transmission loss of the telephone line 12 using the dial signal. The signal reception level of the station 14 can always be maintained below the reference level.

Next, an embodiment will be described in which the input signal of the line transformer 34 whose signal level changes according to the line characteristics of the telephone line 12 is used as it is. As shown in FIG. 3, a level attenuator 32 is provided in place of the sending level adjuster 20, and a bandpass filter 34 and a level determination circuit 36 are provided in place of the detection circuit 22 to automatically adjust the signal sending level. can do.

That is, the level attenuator 32 is provided with a plurality of resistors, and a switch circuit is provided in order to select a specific resistor according to the signal from the level determination circuit 36. Then, as the bandpass filter 34, a filter that passes only the frequency component of the modulated signal transmitted through the signal line 26 is used, and the output level of the filter 34 is determined by a level determination circuit 36 having a plurality of determination levels. The level determination circuit 36 is the fourth
As shown in the figure, a plurality of level determination units 37. , 37□.

..., 37,5.37.6. Each level determination section 37. ,37□,...,37. , correspond to each of the selection operations in FIG. If a resistance selection signal is sent to the level attenuator 32 via the OR circuit 38 to suppress the deviation between the judgment level and the set level for making the reception level below the reference level to zero, the above-mentioned implementation is possible. As in the example, the reception level of the terminal station 14 can always be maintained below the reference level.

In the above embodiment, the transmission level was optimized when making a call, but when the modem is on the receiving side, the modem transmission level is optimized by adjusting the answer back tone returned from the modem when the call is received. The same thing can be done using

〔Effect of the invention〕

As explained above, according to the present invention, the reception level at the signal receiving end can always be maintained below the reference level, making it possible to prevent reception errors and contributing to high efficiency and high multiplication of signal transmission. can contribute.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is a block diagram showing one embodiment of the present invention, Fig. 3 is a block diagram showing another embodiment of the invention, and Fig. 4 is a level judgment circuit diagram. , FIG. 5 is an explanatory diagram of the conventional method, and FIG. 6 is a diagram for setting the sending level setting. 1 to 4, 2 is a level adjustment means (sending level adjuster 20, level attenuator 32), 4 is a level detection means (detection section of the detection device 22, detection section of the level judgment circuit 36), 6 Reference numeral 8 indicates a level specifying means (level specifying section of the detection device 22, level specifying section of the level determining circuit 36), and 8 indicates a switching section (switch 18). Shiheruhan・1st court old Yushi (2) Fig. 4 Sleeper or Bo no Tatsu i11 [] Fig. 5 5 shi ahead\1 next dB)

Claims (1)

[Claims] (1) In a communication terminal device that sends a modulated signal to a line formed by sending a signal to form a line with a partner device, the level of the modulated signal is converted to a predetermined level and a signal transmission line is created. level adjusting means (2) for transmitting signals to the other party; level detecting means (4) for detecting the level at the sending end of the signal for forming the line; A signal sending level setting device comprising level specifying means (6) for specifying a signal sending level for setting the receiving level of the device below a reference level to a level adjusting means.