JPS6133493B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a facsimile apparatus equipped with adjustment means necessary to compensate for transmission losses in telephone lines and the like.

FIG. 1 is a schematic configuration diagram of an image signal transmission system. When transmitting the image signal of the transmission original image in this system, a facsimile device 1 (hereinafter referred to as the transmitting side device) having a transmitting section or transmitting/receiving section
The subscriber number of the other party is dialed using a telephone set 2 connected to the telephone set 2, and this dial signal is sent out via a telephone line 3. When the exchange 4 detects the dial signal, it selects the telephone line 5 corresponding to the subscriber number of the other party, and transmits the facsimile device 6 (hereinafter referred to as the receiving side device) having a receiving section or a transmitting/receiving section to the other party. call. When the receiving device responds, the transmitting device 1 and the receiving device 6 exchange control signals via the telephone lines 3 and 5, and then become ready to transmit and receive image signals. 7 is a telephone.

By the way, regarding the receiving side device 6, the higher the reception level of the image signal from the viewpoint of S/N, etc., the better the reproduced image can be obtained.

However, in reality, the image signal sent from the transmitting device 1 is attenuated by the telephone lines 3 and 5, the exchange 4, etc., and the reception level to the receiving device 6 is the same as the image signal output level of the transmitting device 1. It is very low compared to the current level, and it is affecting the reproduction of the image signal.

Therefore, as the simplest means for increasing the reception level to the receiving device 6, it has been considered to increase the image signal sending level of the transmitting device 1. However, if the telephone lines 3 and 5 constitute a telephone line network for subscriber telephones, the specifications (technical standards) of the exchange 4
Due to problems such as crosstalk on the telephone lines 3 and 5, the output level of the image signal sent from the transmitting device 1 is -15
+L” dBm (where L is the transmission loss of the telephone line 3). Therefore, the transmission level of the transmitting device 1 cannot be increased indefinitely.

Therefore, the most appropriate solution is to measure the transmission loss L of the telephone line 3 in advance and correct the output level of the transmitting device 1 by this loss, which is simple and effective.

Conventionally, compensation for such transmission loss has been performed as follows. In other words, when installing the device, telephone line 3
Then, the transmitting device 1 is disconnected, a level meter is connected to the end of the telephone line 3, and the incoming level of the transmission loss measurement signal sent from the exchange 4 is measured. Then, the transmission loss of the telephone line 3 is calculated from the sending level of the exchange 4 and the incoming call level measured by the level meter. For example, a resistor of the adjusting section is selected and adjusted by soldering so that the output level of the transmitting side device 1 is increased by the transmission loss calculated by this calculation.

However, with such facsimile equipment, it is necessary to bring a level calculation measuring device and a soldering iron to the equipment installation site each time the equipment is installed.
Adjusting the output level is very complicated.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and eliminates the need to bring in a measuring device for level calculation and soldering work, and easily compensates for the transmission loss of telephone lines etc. when installing the equipment. The present invention provides a facsimile device that transmits a modulated signal of an image signal at a suitable transmission level.

An embodiment of the present invention will be described below with reference to the drawings. According to the present invention, a circuit for compensating for transmission loss is provided in the output system of a facsimile apparatus having at least a transmitting section, and a specific example of the apparatus is shown in FIG. In the figure, an image signal for a transmitted original image is input to a modulation circuit 12 via an input terminal 11. This modulation circuit 12 modulates a carrier wave signal with an image signal and sends out a modulated signal. Reference numeral 13 denotes a two-circuit changeover switch, which closes the movable contact piece 13c to the fixed contact 13a side that connects the output part of the modulation circuit 12 when transmitting the modulated signal, and closes the movable contact piece 13c to the fixed contact 13a side that connects the output part of the modulation circuit 12. It is used by closing the contact 13c to the fixed contact 13b side. A movable contact piece 13c of the changeover switch 13 is connected to an input portion of a variable gain transmission amplifier circuit 15 having a variable resistor 14 for varying the output level of the modulated signal. This transmission amplifier circuit 15
The output section is branched into two, and one of the output sections is connected to one fixed contact 16a of a two-circuit changeover switch 16 that can switch in conjunction with or independently of the changeover switch 13.
The other output section is connected to a level comparison circuit 18 via a detection circuit 17. This level comparison circuit 18 has a function of outputting a signal when the output level of the detection circuit 17 is within a certain level range. The output portion of this level comparison circuit 18 is connected via a light emitting diode 19 to one end of a current limiting resistor 20 whose other end is connected to a power supply terminal.
When compensating for transmission loss, this light emitting diode 19
Light is emitted when the detected output level obtained by varying the variable resistor 14 is within the set level range of the level comparison circuit 18.

A changeover switch 16 disposed at one output section of the transmission amplifier circuit 15 closes a movable contact piece 16c to a fixed contact 16a on the output side of the transmission amplifier circuit 15 as shown in the figure when transmitting a modulated signal, thereby reducing transmission loss. When compensating, the ground side fixed contact 16b is closed and used.
Reference numeral 21 indicates a hybrid transformer, to which matching resistors 22 to 24 are connected to one side of the winding terminal (including the intermediate winding terminal), and the other end of the matching resistor 22 is connected to the movable contact piece 16c of the changeover switch 16. In addition, the other matching resistors 23 and 24 are grounded.
A common portion of the hybrid transformer 21 and the matching resistor 22 is connected to the fixed contact 13b side of the changeover switch 13. The other winding side of the hybrid transformer 21 is connected to a line connection terminal 26 via a line connection transformer 25. Although not shown, a telephone line is connected to a line connection terminal 26.

Next, the operation of the facsimile device as described above will be explained. Normally, the changeover switches 13 and 16 are closed toward the fixed contacts 13a and 16a. In this case, the image signal of the transmitted original image is sent to the modulation circuit 12 via the terminal 11.
After being converted into a modulated signal, this modulated signal is sent to a transmission amplifier circuit 15, a changeover switch 16,
The signal is transmitted from the line connection terminal 26 to a telephone line (not shown) through the hybrid transformer 21 and the line connection transformer 25.

When compensating for transmission loss, selector switches 13 and 16
to the fixed contacts 13b and 16b. At this time, the output level adjustment signal transmitted from the exchange through the telephone line arrives at the line connection terminal 26, passes through the transformers 25 and 21 and the changeover switch 13, and is input to the variable gain transmission amplifier circuit 15. here,
The output level adjustment signal is amplified and further detected by a subsequent detection circuit 17, and this detection output is compared with a set level by a level comparison circuit 18. In other words,
This level comparison circuit 18 has a sensitive zone area with a predetermined level width in advance, and has a function of outputting a signal when the detected output level is within this sensitive zone area. The level in this sensitive zone means that the output level of the modulated signal is an appropriate level taking into account transmission loss of telephone lines and the like. When the detected output level is within the sensitive range of the level comparison circuit 18, a signal is output from the level comparison circuit 18 and the light emitting diode 19 emits light. Therefore, by checking the light emitting state of the light emitting diode 19, it can be determined whether the modulated signal is being sent out at an appropriate level from the variable gain transmission amplifier circuit 15 when the modulated signal of the image signal is sent out. .

By the way, the output level adjustment signal sent from the exchange is detected by the detection circuit 15, and the detected output level is compared by the level comparison circuit 18. As a result,
If the level is not within the sensitive zone region, that is, if the light emitting diode 19 does not emit light, the variable resistor 14 is adjusted to vary the gain of the variable gain transmission amplifier circuit 15. By adjusting the variable resistor 14, when the detection output level of the detection circuit 17 falls within the predetermined level range of the level comparison circuit 18, the light emitting diode 19
emits light, so the light emitting state of the light emitting diode 19 is checked, the gain of the variable gain transmission amplifier circuit 15 is fixed, and the compensation for the transmission loss is completed.

Next, an example of actually compensating for transmission loss using numerical values will be described. First, when the device manufacturing is completed, the output level of point A corresponding to the output section of the modulation circuit 12 is adjusted to -3 dBm, and the detection circuit 17 is adjusted to -3 dBm.
The detection circuit 17 is designed to enable the light emitting diode 19 to light up when the B point of the input section of the
It is also assumed that the circuit constants of the level comparison circuit 18 are adjusted.

When the device is installed, the output level adjustment signal from the exchange enters the line connection terminal 26, and is further input to the variable gain transmission amplifier circuit 15 via the line connection transformer 25, the hybrid transformer 21, and the fixed contact 13b of the changeover switch 13. be done.

Now, let the insertion loss of transformers 25 and 21 be zero,
If the transmission loss of the telephone line is also zero, the signal from the exchange will arrive at the line connection terminal 26 at 0 dBm. However, this is when the signal output level of the exchange is set to 0 dBm. This 0 dBm incoming signal passes through the hybrid transformer 21 and appears at the fixed contact 13b side (point C) of the changeover switch 13 as -3 dBm, which is then transmitted to the variable gain transmitting amplifier circuit 15.
to go into. Next, the variable resistor 14 of the variable gain transmission amplifier circuit 15 is adjusted so that the detection output level of the detection circuit 17 falls within a predetermined level range of the level comparison circuit 18, and the subsequent light emitting diode 19 is turned on. At this time, variable gain transmission amplifier circuit 1
The gain of 5 is -3dB.

After completing the above work, switch 13, 1
6 to the fixed contacts 13a and 16a, the output signal of the modulation circuit 12 becomes -6 dBm at point B and -12 dBm at point C (attenuated by 6 dB due to the impedance of the matching resistor 22 and the hybrid transformer 21), and furthermore, The constant loss of the hybrid transformer 21 -3dB is added to the line connection 26.
A signal of 15dBm will be output.

Next, we will discuss the case where the loss of the telephone line, etc. is 10 dB. In this case, the changeover switch 13,
16 to the fixed contacts 13b and 16b. A -10dBm signal arrives at the line connection terminal 26,
At point C, the signal becomes -13 dBm and is input to the variable gain transmission amplifier circuit 15. At this time, if the variable resistor 14 is adjusted to cause the light emitting diode 19 to emit light, the gain of the variable gain transmission amplifier circuit 15 will be +7 dB.

Thereafter, when the changeover switches 13 and 16 are closed to the fixed contacts 13a and 16a and an image signal is supplied to the terminal 11, the modulated signal of the modulation circuit 12 becomes (-3
+7-6-3)=5dBm and line connection terminal 2
6 is sent out.

By adjusting the gain of the variable gain transmitting amplifier circuit as described above, the loss of the transmission line is compensated for,
The output level can be set to the upper limit of the output level limited by (-15+L) dBm.

Therefore, even if the transmission loss of a telephone line or the like has an arbitrary value, the facsimile apparatus of the present invention can reduce the amount of damage by varying the gain of the variable gain transmitting amplifier circuit 15 and adjusting the light emitting diode 19 to emit light. The sending level of the modulated signal can be sent as a value that compensates for line loss.

It goes without saying that the present invention is not limited to the above embodiments. That is, in the above embodiment, the variable resistor 14, which requires manual operation, is used as the gain variable means of the variable gain transmission amplifier circuit 15, but for example, a slide resistor may be used instead of the variable resistor 14. It is also possible to provide this and automatically vary it by the detection output of the detection circuit 17. In this case, the output level of the device can be adjusted without requiring human intervention. Further, although the level comparison circuit 18 has a function of comparing and determining whether or not the detected output level is within a predetermined level range, such a function is not necessarily necessary. It may also have the function of setting a signal and outputting a signal if the detection output level is equal to or higher than the set level. Further, although the light emitting diode 19 is made to emit light to confirm the output level of the device, a meter or a speaker may be used instead of the light emitting diode 19. In addition, it goes without saying that the present invention can be modified in various ways without departing from the spirit thereof.

As described in detail above, according to the present invention, the amplifier circuit used when transmitting the image signal is normally of a variable gain type, and the output section of the variable gain amplifier circuit is provided with a level comparison means, a light emitting element, etc. The structure is such that the output level of the variable gain amplifier circuit is adjusted while the gain is varied, and the light emitting element is made to emit light.When the equipment is installed, it is easy to make adjustments on the equipment side by simply receiving a signal for adjusting the output level from the exchanger. The modulated signal of the image signal can be sent out at a sending level that compensates for transmission loss.

Therefore, this device allows you to easily adjust the output level without having to bring in a level meter or perform soldering work each time you install the device.
Equipment installation time can be significantly reduced. In addition, we provide a facsimile device that can easily adjust the transmission level even if the transmission loss of a telephone line or the like has an arbitrary value, and can automatically adjust the transmission level without requiring human intervention by using the detection output level. can.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of a facsimile image signal transmission system, and FIG. 2 is a block diagram showing an embodiment of a facsimile apparatus according to the present invention. 12... Modulation circuit, 13... Changeover switch, 1
4... Variable resistor, 15... Variable gain transmission amplifier circuit, 16... Selector switch, 17... Detection circuit, 18... Level comparison circuit, 19... Light emitting element, 21... Hybrid transformer, 22... 24
... Matching resistor, 25 ... Line connection transformer, 26 ... Line connection terminal.

Claims (1)

[Claims] 1 In a facsimile device connected to an exchange or the like via a line, there is a modulation circuit that generates a facsimile modulated signal of a predetermined level, and a modulated signal from this modulation circuit or input via the line connection terminal of the device output section during adjustment. a switching means for selecting a level adjustment signal sent from an exchange or the like to be adjusted; a variable gain amplifier circuit for amplifying the signal inputted via the switching means; and a variable gain amplifier circuit for amplifying the signal input via the switching means; A facsimile device comprising: a circuit that outputs a signal when the signal level is at a predetermined level; and a notification means that operates based on the output signal of the circuit and notifies that the signal level of the variable gain amplifier circuit is at the predetermined level. .