JP2759964B2 - Facsimile machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a facsimile apparatus, and more particularly to a facsimile apparatus capable of simplifying a protocol and shortening a communication time.

(Prior Art) In a facsimile apparatus, a signal received through a line is input to a modem via an NCU, and a signal input to the modem is demodulated and stored in a buffer memory, and further passed through a decoding circuit and the like. Output to the printer device. In a conventional facsimile machine, the level of a signal that can be detected by the modem is set within a certain range. The lower limit of the range is set to a relatively low level so that signals of a wide range of levels can be received.

(Problems to be Solved by the Invention) The above-described conventional technology has the following problems.

That is, in the prior art, a signal of a wide range of levels is configured to be received, but on the other hand, even low-level noise may be detected as a signal. For this reason, in the protocol control between the facsimile apparatuses, there is a problem that a correct signal is not recognized due to the noise and a communication time becomes longer.

In addition, when the signal level is extremely large, the signal is distorted and a data error occurs, so that a correct signal is not recognized, the protocol time is wasted and the communication time is lengthened. there were.

SUMMARY OF THE INVENTION An object of the present invention is to provide a facsimile apparatus which eliminates the above-mentioned problems of the prior art, simplifies a protocol and shortens communication time.

(Means and Actions for Solving the Problems) In order to solve the above problems and achieve the object, the present invention provides an incoming signal level detection means for a signal input to a modem, Means for comparing the signal level and the lower limit of the signal detection level range of the modem; level adjusting means for changing the level of the signal input to the modem; and means for changing the detection level of the carrier detector. And based on the comparison result of the comparing means, one of the signal amplification factor of the adjusting means and the detection level of the carrier detector is within the range of the signal detection level of the modem, and the input signal is set to the lower limit thereof. It is characterized in that the level is adjusted to be close to each other.

Further, the present invention provides a facsimile apparatus which continues to output a call signal at a scheduled time after dialing, and means for determining whether or not there is a signal for the call signal, and changing a level of a signal input to a modem. And a timer for counting a time shorter than the scheduled time, and the timer for counting the call signal by the end of counting the timer value. When there is no response signal, the configuration is such that any one of the signal amplification factor of the signal level adjusting means and the detection level of the carrier detector is changed every time the time set in the timer elapses. There is.

According to the present invention having the above configuration, the signal level can be reduced to a value within the detection level range of the modem and near the lower limit value of the level range in accordance with the incoming level of the signal. Also, depending on the incoming signal level,
The detection level of the modem can be adjusted to bring the detection level of the modem closer to the signal. As a result, noise at a lower level than the signal whose level is detected first is not received.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention.

In FIG. 1, a buffer amplifier 1 amplifies a signal input from a transmission line.
The signal amplified by the modem 3 is passed through an adjusting means 2 having amplifiers 2a to 2e for adjusting the level of the signal.
Is input to

The signal input to the modem 3 is A / D converted by the A / D converter 4, transferred to the signal processing unit 5 and demodulated. Also, A /
The output signal of the D converter 4 is input to the modem processor 7, and the level of the signal can be detected. The AGC circuit 6 is a circuit that automatically adjusts the gain according to the level of the signal detected by the modem processor 7 and keeps the signal input to the A / D converter 4 constant.

The carrier detector 8 monitors the level of the signal received from the transmission line, and if the level is below a specified value (hereinafter referred to as a lower limit, which is usually -43 dBm), the received signal is correctly received. Output a signal indicating that no

The input signal level from the transmission line detected by the modem processor 7 is input to the comparison operation means 10 of the controller 9. The comparison operation means 10 compares the level of the signal input from the transmission line with the lower limit of the signal detection level of the carrier detector 8 and calculates the difference between the two levels. The level of the signal input from the transmission path is within the range of the signal detection level of the carrier detector 8 (0 to 0).
One of the amplifiers 2a to 2e of the adjusting means 2 is selected by the amplifier selecting means 11 so as to have a value close to the lower limit of -43 dBm). Note that the controller 9 can be constituted by a microprocessor.

Next, the operation of this embodiment having the above configuration will be described. In FIG. 1, first, at the start of signal reception, the buffer amplifier 1 and the modem 3 are connected via the amplifier 2d (amplification factor "0") of the adjusting means 2. Therefore, the signal input from the transmission path via the buffer amplifier 1 is input to the modem main body 3 without changing the input level by the adjusting means 2.

The level of the output signal from the A / D converter 4 detected by the modem processor 7 is input to the comparison operation means 10 and compared with the signal detection level of the carrier detector 8 to calculate the difference.

Here, for example, when the lower limit of the signal detection level range of the carrier detector 8 is −43 dBm and the incoming level of the signal input from the transmission path is −30 dBm, the difference between the signal detection level and the incoming level is 13 dBm. . The difference 1
3 dBm is reduced, and the incoming signal level (−30 dBm) is made closer to the signal detection level (−43 dBm) of the carrier detector 8,
Further, any one of the amplifiers 2a to 2e of the adjusting means 2 is selected so as to adjust to a value higher than the signal detection level.

The signal of -30dBm is brought close to -43dBm, and -43dBm
To adjust to a higher value, one of the amplifiers 2a to 2e
2b is selected. Since the amplifier 2b has a gain of -10 dB (attenuation of 10 dB), the input signal of -30 dBm is -4 dB.
Attenuated to 0 dBm. Once the amplifier 2b is selected,
All signals input from the transmission line are attenuated by 10 dB. Similarly, the noise level is also attenuated by 10 dB,
Most of the low-level noise is attenuated below the lower limit of the signal detection level of -43 dBm. Therefore, the noise of 0 to -43 dBm input to the modem 3 when the amplifier 2d is selected, the noise of only a narrow range of 0 to -33 dBm is input after the amplifier 2b is selected. , Almost no noise above the signal detection level is input to the modem 3.

Next, the detection of the level of the signal input from the transmission line and the timing of the level adjustment of the signal will be described with reference to the protocol example shown in FIG. In FIG. 2, when dialed from the transmitting side, the called side identification signal CED is transmitted from the receiving side several seconds later, and then the flag F1 and the digital identification signal DIS are transmitted. The transmitting side transmits the called station identification signal C
When recognizing the ED, the flag F1, and the digital identification signal DIS, it sends a flag F2 and a digital command signal DCS, and then sends a training check signal TCF.

As described above, the flag F2 and the digital command signal DCS output from the transmission side are output after recognizing the called station identification signal CED, the flag F1, and the digital identification signal DIS output from the reception side. If noise is mixed in the identification signal sent from the receiving side during this communication, the transmitting side will have difficulty in recognizing the identification signal, and the protocol will be complicated, and extra time will be required.

Therefore, in this embodiment, when the called station identification signal CED sent from the receiving side is input to the modem 3 on the transmitting side, the level of the identification signal CED is detected by the modem processor 7. Then, a comparison with the detection level of the carrier detector 8 is performed by the comparison operation means 10, and based on the result, an amplifier having an appropriate amplification factor is selected from the amplifiers 2a to 2e. After an appropriate amplifier is selected, the risk of receiving noise is reduced because the modem does not detect a signal lower than the level of the identification signal CED, and the protocol control is performed efficiently.

On the other hand, the receiving side identifies the flag F2, the digital command signal DCS, and the training check signal TCF transmitted from the transmitting side, and transmits the flag F3 and the reception preparation completion signal CFR. The level of the flag F2 is detected, and the amplifier of the adjusting means is selected based on the result.

Next, a second embodiment of the present invention will be described. FIG. 3 is a block diagram showing the configuration of the second embodiment. In the figure, the same symbols as those in FIG. 1 represent the same or equivalent parts.

In the figure, the level of the signal input from the transmission line is detected by the modem processor 7 based on the output of the A / D converter 4, and the result is compared with the comparison operation means of the controller 11.
Entered in 10. The comparison operation means 10 compares the level of the input signal with the signal detection level of the carrier detector 8. Then, based on the difference between the two levels, the threshold value calculating means 12 calculates a threshold value for changing the range of the signal detection level of the carrier detector 8, and the calculation result is used as the signal detection level range. It is set in the detector 8.

In the threshold value calculating means 12, the lower limit value of the signal detection level range of the carrier detector 8 is close to the level of the signal input from the transmission line detected by the modem processor 7, In addition, calculation is performed according to a calculation table (not shown) set as a ROM value so as to be a low value.

As described above, in the second embodiment, the detection level of the carrier detector 8 can be adjusted in accordance with the level of the signal input from the transmission line, so that a signal lower than the level of the signal detected first is received. As a result, the risk of receiving noise can be greatly reduced.

In the second embodiment, as in the first embodiment, the level of the signal input from the transmission line is detected by detecting the levels of the identification signals transmitted first from the transmission side and the reception side. Will be

Next, a third embodiment of the present invention will be described. FIG. 4 is a block diagram showing a third embodiment. In the figure,
The presence / absence of the output of the A / D converter 4 is detected by the signal presence / absence detection means 13 of the controller 17. First timer 14 and second timer
The timer 15 starts counting the set timer value after the completion of dialing for communication. The set value of the first timer 14 is shorter than the set value of the second timer 15. Is set.

Until the signal presence / absence detection means 13 detects an output signal, the amplification command means 16 outputs an amplification command to the adjustment means 2 every time the first timer 14 finishes counting. The adjusting means 2 performs an operation of switching the currently connected amplifier to an amplifier having a higher one-stage amplification factor in response to the command.

Detection operation by the signal presence / absence detection means 13, first timer
The counting and the amplifier switching operation of 14 are continued until a signal is detected by the signal detecting means 13 or until the counting of the second timer 15 is completed.

Next, the operation of the third embodiment will be described with reference to the flowchart of FIG. In the third embodiment, an amplifier having a negative amplification factor, for example, the amplifier 2b is selected so that the level of the input signal is attenuated by the adjusting means 2 at the start of communication. In the figure, in step S1, dialing for issuing a call signal to the other party is performed. By the dial operation, the call signal is continuously output for the counting time of the second timer 15.

In step S2, counting by the second timer 15 is started, and in step S3, counting by the first timer 14 is started. Steps
In S4, the presence / absence of a signal input from the transmission path is determined by the signal presence / absence detecting means 13. If the determination in step S4 is affirmative, the amplifier of the adjusting means 2 is not switched,
Communication is performed as it is.

If the determination in step S4 is negative, the second
It is determined whether or not the counting of the scheduled time by the timer 15 has been completed (step S5). Until the counting by the second timer 15 is completed, the process proceeds from step S5 to step S6. Steps
In S6, it is determined whether or not the scheduled counting by the first timer 14 has been completed. Step until the scheduled time has elapsed
Returning from step S6 to step S4, the presence / absence of an input signal is monitored by the signal presence / absence detecting means 13.

If the input signal is not detected by the signal presence / absence detecting means 13 even after the time set in the first timer 14 has elapsed, the process proceeds from step S6 to step S7,
In accordance with the command signal output from 16, the amplifier of the adjusting means 2 is switched to an amplifier having an amplification factor one step higher. For example, if the amplifier 2b was selected before,
The amplifier is switched to the amplifier 2c having a large one-stage amplification factor.

The above operation is repeated until the time set in the second timer 15 elapses or until an input signal is detected in step S4. In step S5, the second
When the counting by the timer 15 is completed, the process returns to step S1 and dialing is performed again. Then, once the input signal is detected, communication is performed while the amplification factor of the adjuster 2 is maintained at the current state.

As described above, according to the third embodiment, the signal that has been attenuated and input is gradually amplified until it is detected by the modem, and then amplified when the signal is detected. The rate is fixed. Therefore, communication can be performed in a state where the level of the input signal and the signal detection level of the modem are close to each other, so that low-level noise is not received.

As a modification of the third embodiment, the carrier detector 8
Means for changing the signal detection level of the carrier detector 8 at the start of communication, the signal detection level of the carrier detector 8 is set to be higher, and the signal detection level is changed every time the time set in the first timer 14 elapses. The detection level of the carrier detector 8 may be reduced by the means, and the detection level may be fixed when an input signal is detected.
The same effects as in the third embodiment can be achieved.

Further, in the processing of the third embodiment, after an input signal is detected, the same processing as that described in the first and second embodiments may be performed. That is, after the input signal is detected, the incoming level of the signal is detected, and the level of the signal input to the modem is adjusted or the detection level of the carrier detector is changed according to the result. Should be controlled.

In the first and second embodiments, the level of the signal input from the transmission line is compared with the detection level of the carrier detector 8, and based on the result, the input level of the signal and the detection of the carrier detector 8 are detected. Changed one of the levels.

On the other hand, in the third embodiment, at the start of communication, the amplification factor of the adjusting means 2 is set to a lower level, or the detection level of the carrier detector 8 is set to a higher level. Then, after dialing for communication, it is determined whether or not there is a signal responding to the dial. Each time, the gain of the adjusting means 2 is gradually increased, or the detection level of the carrier detector 8 is gradually reduced.

As described above, according to the above embodiment, since the level of the signal input from the transmission line and the signal detection level of the modem can approach each other, low-level noise is not received.

(Effects of the Invention) As is clear from the above description, according to the present invention, the following effects can be achieved.

(1) Since the reception of noise can be reduced, it becomes easy to identify the signal in the protocol, and as a result, there is no useless time in the protocol.

(2) Since the signal can be amplified or attenuated according to the level of the signal, even if the incoming level of the signal is extremely high, the signal is not distorted and a data error does not occur.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a flowchart showing an example of protocol control, FIG. 3 is a block diagram showing a second embodiment, and FIG. 4 shows a third embodiment. FIG. 5 is a flowchart showing the operation of the third embodiment. 2 ... Signal level adjusting means, 2a ~ 2e ... Amplifier, 3 ...
Modem 7, Modem processor 8, Carrier detector 9, Modem controller 10, Comparison operation means,
11 ... Amplifier selection means, 12 ... Threshold calculation, 13 ... Signal presence / absence detection means, 14 ... First timer, 15 ... Second timer, 16 ... Amplification command means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04M 11/00-11/10 H04N 1/32-1/36

Claims (2)

(57) [Claims] 1. A facsimile apparatus for outputting a call signal continuously for a predetermined time after dialing, a means for determining the presence or absence of a signal responding to the call signal, and changing a level of a signal input to a modem. A level adjusting means for counting a timer value shorter than the scheduled time; and a means for judging the presence or absence of the signal until the counting of the timer value is completed. Within the predetermined time, every time the timer value is counted, an amplifier having a larger one-stage amplification factor is selected from amplifiers provided in the signal level adjusting means and having a plurality of stages of amplification factors and input to the modem. A means for amplifying the level of a signal to be transmitted. 2. A facsimile apparatus for outputting a call signal continuously for a predetermined time after dialing, means for judging the presence or absence of a signal responding to the call signal, and a timer value shorter than the predetermined time. A timer for counting the timer value, and when it is determined that there is no call signal by the means for determining the presence or absence of the signal until the end of counting the timer value, the carrier is carried out every time the timer value is counted within the scheduled time. Means for reducing the detection level of the detector by a predetermined level.