FR2525057A1 - FAX SYSTEM - Google Patents

Abstract

THE INVENTION RELATES TO A FAXING APPARATUS IN WHICH, IN ORDER TO VERIFY THAT A RECEIVER CAN PROPERLY RECEIVE AN IMAGE TRANSMITTED FROM A TRANSMITTER, A CHECK SIGNAL OF A PREDETERMINED IMAGE CONFIGURATION IS TRANSMITTED AND RECEIVED BEFORE TRANSMISSION OF THE IMAGE OF AN ORIGINAL. A CONTROL DEVICE 114 SELECTS, DEPENDING ON THE RECEIVED CONTROL SIGNAL, ONE OF THE THREE IMAGE TRANSMISSION METHODS, SO THAT THE QUALITY OF THE RECEIVED IMAGE IS DEGRADED AS LESS AS POSSIBLE BY THE CHARACTERISTICS OF THE TRANSMISSION LINE. THE CHOICE OF PROCESS IS ALSO DETERMINED BY THE SIZE OF THE ORIGINAL AND THE RECORDING PAPER. FIELD OF APPLICATION: FAX OF DOCUMENTS, ETC.

Description

252505?

  The invention relates to a facsimile system

  able to select one of several processes

  transferred different from image transmission, depending on

  the state of a transmission line concerned.

  It is well known that a fax system

  to GIII standards (digital type), in accordance with the

  CCITT T 4, is a fax system capable of

  to change the speed or method of transmission according to the state of a transmission line In such a system, before the transmission of a high-speed image, an automatic equalizer associated with a receiver is controlled by signals and control signals according to the characteristics of the transmission line.

  order results are then discredited.

  to determine the speed and method of transmission If the automatic equalizer can not be satisfactorily controlled, an error signal is generated to disconnect the line or the transmission circuit Such a facsimile system is expensive and is therefore available in the trade in the form

  a sophisticated circuit, high price.

  On the other hand, it is known that a fax system of the type GII (analog type), in conformity with the

  recommendation T 3, is an intermediate class system

  low price However, a tele-

  copy GII requires a transmission time of about three

  times higher than that requested by a system of

  Thus, widely used high speed analog facsimile systems having a transmission rate equivalent to that of a high speed and inexpensive system. An example of a conventional high-speed analog facsimile system, and an example of image degradation that can be caused by such a system due to the characteristics of the detection circuit of a line of

  transmission, will now be described.

  A first image transmission method in which the amount of data is briefly described will be briefly described.

  images to be transmitted is ordered according to the

  black and white born of an image to be transmitted The transmitter divides into M blocks a set of L-bit image signals corresponding to an image line and received from an analyzer, if the number of elements of images included in a block is represented by N, L = M x N (where L, M and N are all integers) The image signal included in each block is controlled If a block consists entirely of one white signal, an N-bit jump signal

  is modulated and put in place of the N-bit image signal.

  If the block comprises more than one bit of the black signal, the N bit image signal is modulated and transmitted. It should be noted that N> N and N axb, oa and b are integers. It is preferable that N> 1 It's like that

  because the jump signal has a specific meaning

  that in the method described, in the method AM-PM-VSB or PM-DSB, used as analog transmission method, the error rate is noticeably high. Therefore, if N = 1, a correct image may not be received, in the practical sense A bit synchronization signal is

  added at the beginning of each line, o Z is a multiple

  Thus, 9> to n In this case, a jump signal is a combination of N-bit signals in which a signal of an amplitude greater than the maximum amplitude of the image signal (hereinafter referred to

  high level signal ") is maintained during a certain

  then a zero amplitude signal of the image signal is present A synchronization signal is an x bit signal in which a high level signal, of a duration greater than that of the jump signal, is

  followed by a zero amplitude signal of the image signal.

  The transmitter having the configuration indicated below

  above module and transmits an image data signal in which a 9-bit sync signal is added at the beginning of each line and jump signals are embedded in blocks including all

white signals.

  The receiver demodulates the received sequence signal

  to produce a baseband signal The receiver controls the amplitude of the baseband signal in order to discriminate between the signal

  image and synchronization and jump signals.

  The receiver then controls the duration (time interval before the zero level signal) of the high level signal to discriminate between the sync signal and the jump signal. The receiver discriminates between the jump signal and the signal. image signal at the moment of receiving the nth bit from the time of reception of the synchronization signal

  signal emitted by the first method of im-

  will now be described in more detail with reference to the accompanying drawings. FIG.

  emitted signal Line a in Figure 1 shows a confi-

  image signal guration for a line, which is a

  binary signal having two levels of black and white.

  It should be noted that a line has 256 bits and a block has 64 bits Thus, a line is divided into four blocks If we assume that only the third block contains a black signal, the emitted signal has a structure as shown in line b of the

figure 1.

  Before the transmission of data on a line, a synchronization signal is transmitted Since the first block is a completely white block, a jump signal is transmitted in correspondence with this block Since the second block is also a block entirely white, another jump signal is emitted The third block comprises a black signal and the image signal is therefore transmitted A guardband signal is generated before the transmission of the current image signal only

  if the immediately preceding block is a jump signal.

  The guardband signal is generated to prevent adverse fringe effects of the trailing edge of the immediately preceding jump signal having an amplitude

  double, on the leading edge of the current image signal.

  The 64-bit image signal of the third block is transmitted after the guard band signal Since the fourth block is also a wholly blank signal, a jump signal is transmitted, thereby completing the

transmission of a line.

  Figures 2A, 2B and 2C show the structures

  The synchronization signal, as shown in FIG. 2A, is a 56-bit signal having a high level duration of 46 bits, a duration of black signal level of 5 bits, and a

  5-bit blank signal level duration, in the or-

  The jump signal, shown in FIG. 2B, is an 8-bit signal comprising a high level duration of 6 bits and a duration of the level of the 2-bit black signal. The guardband signal is , as

  represented in FIG. 2C, an 8-bit signal comprises

  a 3-bit black signal level duration and a 5-bit blank signal level duration Since the transmission rate is 7740 bits per second in this case, the duration of the level part

  high of the sync signal is 5943 microseconds

  condes, while that of the jump signal is 775 microseconds.

  Figure 3 is a simplified diagram of the reception

  A block 10 comprises a network control unit NCU and an equalizer. The latter is of the fixed type and serves to correct the attenuation and the delay distortion of a telephone line, to a certain extent.

  output signal from the set 10 NCU / equalizer is applied

  to a signal line i Qa A telephone line l Ob

  is connected to the input end of the NCU / equalizer 10.

  An automatic gain control circuit (hereinafter referred to as "AGC control circuitry") 12 is connected to the output end of the NCU / equalizer 10 via the line signal: a fax signal originating from the transmitter is attenuated by the telephone line l Oa, used as a transmission medium.

  mission, before arriving at the receiver The degree of

  varies according to each established telephone line.

  Once the telephone line is established, the

  the attenuation remains the same until the end of

  the transmission carried out by this telephone line.

  Therefore, each time a facsimile transmission is performed, the received facsimile signal must be amplified to a certain level by the AGC circuit 12. A facsimile signal amplified to a certain level by the AGC circuit 12 is generated on a circuit. signal line 12a The AGC circuit 12 receives an output signal from a demodulator 14, via a signal line 14a, as a reference signal to perform the automatic gain control operation. AGC circuit 12 also receives, via a signal line 16 e from a signal discriminator 16, a synchronization signal for determining the time at which the automatic gain control operation is performed. The AGC circuit 12 used in this example performs the so-called fast-acting automatic gain control operation; it controls the gain so that the output peak value of the demodulator 14 is only 5 volts, while the received input signal

  by line 16 e signal is at logic level "1".

  When the input signal received via the signal line 16 e is at logic level "O", the

  AGC circuit 12 retains the immediately preceding gain.

  The demodulator 14 may be a demodulator

  AM-PM-VSB and it can be of known configuration.

  The demodulator 14 extracts the carrier of the

  facsimile signal received from the AGC 12 circuit through

  signal, it performs a synchronous detection and a full wave rectification, and it produces on the signal line 14a the signal of

received baseband resulting.

  The signal discriminator 16 is an important part of the overall circuit Although the function of this signal discriminator 16 is described in detail with reference to its simplified scheme, it can be said that the signal discriminator 16 discriminates between the signal discriminator 16 and the signal discriminator 16. synchronization signal, the jump signal, the image signal and the guardband signal and that it transmits these signals on the lines 16a, 16b, 16c and 16d, respectively At the same time, the signal discriminator 16 produces a binary image signal from the received baseband signal and it

  apply this signal on a line 16 f When the discrimination

  The timer 16 detects that the synchronization signal is received, it produces a logic level signal "1" on line 16 e for only the duration of the reception of the synchronization signal. This is the reason why

  the AGC circuit 12 performs an automatic control operation

  gain during the period of time during

  which the synchronization signal is received.

  Upon detecting each of the various signals, a circuit 18 controls a dual buffer memory 26, described hereinafter, via a signal line 18a, so that the image information is placed in that signal.

double buffer 26.

  In response to a signal present on a line 20a, a printer 20 extracts image information or image signal data stored in the double buffer memory 26 via a data line 26a. ,

and print the resulting image.

  A synchronization clock generator 22 determines the times at which the discriminator 16 of

  signal and a byte buffer 24 are activated.

  The synchronization clock generator 22 generates, on a signal line 22 a, identical clock pulses to the synchronization clock pulses.

  bits of the transmitter, that is, clock pulses

  with a frequency of 7740 Hz, and it also generates

  on a signal line 22 b, impulses of hor-

  lodge having a speed higher than that of the pulses

  Bit synchronization clock of the transmitter, that is-

  ie clock pulses having a frequency of

62.5 kHz.

  The byte buffer 24 includes a serial input / parallel output shift register. In response to the bit synchronization clock pulse received via the signal line 22a, the byte buffer 24 is read out. image information

  binary received from the signal discriminator 16 through

  Line 16 f Buffer 24 produces informa-

  8-bit image on a 24-line signal line.

  The double buffer 26 is capable of memorizing

  image information corresponding to two lines

  and so it can include two 256-bit buffers.

  Figure 4 is a diagram of the discriminator 16

  signal comparators 30, 32 and 34 memorize

  respectively V, Vs and V reference voltages These comparators 30, 32 and 34 compare the band signal of

  base received at reference signals VH, VZ and VP), respec-

  and they produce binary signals as

  that results of comparisons, on lines 30a, 32a.

  and 34a, respectively, of signals. It should be noted that VH> VZ> Vp When the comparator 30 produces a logic level signal "11 on the signal line 30a at the detection of the high level signal indicated in FIGS. a at 2c, this means the reception of the high level signal Furthermore, when the comparator 30 produces a logic level signal "O" on the signal line 30a, this means that the input signal is not

  the high level signal The comparator 32 is used to detect

  the level of the black signal as shown in Figure 2b When the signal line 32a is at the logic level "O", it means that the level of the black signal or a black dot is detected at the end The comparator 34 produces, on the signal line 34a, a logic level signal "1" corresponding to the level of the blank signal or a signal of the signal. logical level "O" corresponding to the signal level

black.

  When the signal on line 30a is

  at logic level "1", a counter 36 counts the pulses

  Thus, counter 36 counts the duration of the high level signal. In this example, when the high level signal is prolonged for a duration of 384 ps or more, a line 36 a signal rises or goes from logic level "O" to logic level '1' When the high level signal continues for a duration of 2048 ps or more, a signal line 36 b goes from logic level "O" At the logical level "1" Since the clock pulses received by the signal line 22 b have a period of 16 ps, a duration of 384 ps corresponds to 24.

  synchronization clock pulses received by the

  term of line 22b, while a duration of

  2048 ps corresponds to the reception of 128 pulses of hor-

  synchronization box via line 22 b As has been described for the transmitted signal, the high level of the jump signal has a duration of 775 ps, while the high level of the jump signal has a duration of 775 ps.

  synchronization signal has a duration of 5943 ps.

  When the signal line 36a is at logic level "1",

  this means that the jump signal or the sync signal

  When signal line 36 b is at logic level "1", this means

  that the synchronization signal is being received

  tion. A multiplexer 38 selects one of the signals

  present on exit lines 32a and 34a, respec-

  comparators 32 and 34, and produces the form

  inverted signal selected on a line 38 a signal.

  The signal chosen by the multiplexer 38 between the two signals depends on the logic level of the line 16 e of

signal of a flip-flop 40.

  When the signal line 36 b goes from logic level "O" to logic level "1", flip-flop 40 is set and produces a logic level signal "1"

on line 16 e.

  When the signal line 36a goes from logic "0" to logic "1", a flip-flop 42 is positioned. Thus, flip-flop 42 produces a logic level signal "1" on a signal line 42a and a signal.

  logic level signal "O" on a signal line 42 b.

  Thus, when the signal line 16 e of flip-flop 40 is at logic level "1", this confirms that the synchronization signal is being received.

  42 th line of signal flip-flop 42 is at the logic level

  that "1", this confirms that the jump signal or the synchronization signal is being received. The lines 42a and 42b of the flip-flop 42 have opposite states; line 42a is at the logical level "O" when the line

  42b is at logic level "1", and vice versa.

  A D-type flip-flop 44 is set or repositioned according to the level of the input signal received via line 42a when the input signal received via line 38a passes from the logic level. O "at logic level" 1 "When the input signal present on line 42a is at logic level" 1 ", flip-flop 44 of type D produces a logic level signal" 1 "on line 16b. input signal present on line 42a is at logic level "O", flip-flop 44 produces a level signal

logical 'O' on line 16 b.

  A D-type flip-flop 46 is set or repositioned according to the level of the input signal received via line 16 e when the input signal received via line 38a passes from the logic level. O "at the logic level" 1 "The D-type flip-flop 46 produces an output signal on the signal line 16a; line 16a is at logic level "1" when flip-flop 46 is set, and is at logic level "" when flip-flop 46 is repositioned. A counter 48 counts the bit synchronization clock pulses received via the signal line 22a. An output of the counter 48 is erased by a reset pulse received via a line 60a. signal every time

  that the counter 48 has 8 sync clock pulses

  bits, it produces a logically level signal

  as "1" on a signal line 48a Thus, the byte synchronization clock pulse, which is the same as that used in the transmitter, is generated on

line 48 a signal.

  The circuit further comprises an OR gate 50, an AND gate 52, an OR gate 54 and a delay circuit 56 which consists of a plurality of latches. The delay circuit 56 delays a clock pulse, received through the gate. of the signal line 16 c, the input information received via the signal line 16 b, and it delivers the delayed information on the line

16 d signal.

  When the synchronization clock pulse

  bit rate received via line 22a goes from logic "" to logic "1", a D-type flip-flop 58 blocks the received information through a signal line 54a, and outputs

  the information blocked on the signal line 16 c.

  An impulse generator 60 comprises a monostable multivibrator or the like. When the output of the flip-flop 58 of the type D changes from logic level "O" to

  logic level "1", the generator 60 generates pulses

  have a width of several microseconds on

a line 60a of signal.

  The signal present on the line 18b is produced by means of the control circuit 18 represented on the

figure 3.

  When information intended to discriminate between the synchronization signal, the jump signal, the guardband signal and the image signal is received via lines 16a, 16b, 16c and 16 d, respectively, of the signal discriminator 16, the control circuit 18 produces an erase pulse on the signal line 18b In response to this erase pulse, the flip-flops 40, 42, 44, 46

  and 48 are reset simultaneously.

  The configuration of the signal discriminator has been described with reference to FIG. 4, but can be summarized as follows. By controlling the received baseband signal through line 14a to detect the duration of the signal high level and detect the presence or absence of the signal level of

  black, the signal discriminator 16 discriminates

  between the synchronization signal, the signal of

  jump, the guardband signal and the image signal.

  The discriminator 16 produces the results obtained on

  lines 161a, 16b, 16c and 16d of signals.

  When a signal discrimination operation is completed, the line 16c goes from logic level "O" to logic level "1". At this time, the levels of the remaining lines 16b, 16c and 16d of signals are determined. four types of signals thus obtained are discriminated according to the algorithm designated in Table 1

below.

TABLE 1

  in this table, the mark "x" means that the level

can be 'O' or '1'.

  The mode of operation of the receiver having the configuration indicated above will now be

  described with reference to the timing diagram of FIG.

  Line a of Figure 5 shows the structure of the received signal. Line b shows a baseband signal transmitted on the transmitter side, and this signal also corresponds to the baseband signal received on the side of the transmitter.

receiver.

  When the synchronization signal begins to be received, the comparator 30 signal line 30 rises to the logic level 1 1 ", as indicated in line d of FIG. 5, indicating that the high level signal is in progress. When the reception of the high level signal is continued, the counter 36 counts the duration of the high level signal When the counter 36 reaches the count of 24 clock pulses, that is to say

  after about 384 μs, the D-type flip-flop 42 is posi-

  as shown in Si in line h of Figure 5,

  and the signal line 42a is at logic level "l".

  When counter 36 reaches a count of 128 clock pulses, flip-flop 40 of type D is set, and line 16a goes to logic level "1", as indicated at 52 on line g of FIG. that the signal line 16 e is kept at logic level "1" during 16 c 16 to 16 b 16 d Signal name 1 1 1 x Synchronization signal (SY) 1 O 1 x Jump signal (SKP) 1 OO 1 Watchband signal (GRD) OO Image signal (PIX) this interval, the AGC 12 controls the gain so that the maximum level of the baseband signal received can not exceed 5 volts (line c of the FIG. 5) Since the output 50a of the OR gate 50 shown in FIG. 4 is at the logic level "O" during this interval, the output 52a of the AND gate 52 goes to

  logical level "" Since the exit from the

  Cule 46 of type D is also at logic level "O",

  the flip-flop 58 of the D type is kept repositioned.

  Therefore, the signal line 16c of the D-type flip-flop 58 is held at the logic "0" level. Since the 16 th line is at the "1" logic level during this interval, the multiplexer 38 selects the comparator output. 34 and produces an inverted form of the signal

selected.

  When the signal line 34a of the comparator 34 goes to logic level "O, as indicated in 53 to

  line f of Figure 5, a black dot is detected.

  Signal line 38a then changes from logic level "O" to logic level "1", and flip-flops 44 and 46 of type D are set accordingly. Signal line 16a of flip-flop 46 switches to logic level. 1 ", and the line

  54 of gate OR 54 goes to logic level "1".

  that the next bit synchronization signal is generated on line 22a, as indicated at 54 on line L of FIG. 5, flip-flop 58 of type D is set,

  and the detection of the synchronization signal is signaled

  At this time, the lines 16a and 16b are at the logic level "1". Although this is not shown, since the signal line 16 d of the delay circuit 56 is at logical level "O",

  the synchronization signal is detected.

  Although the synchronization signal comprises 56 bits, it is detected at the instant of the 48th bit. When the synchronization signal is detected, the counter 36 and the flip-flops 40, 42, 44, 46 and 58 are repositioned by the pulse. erasure from the circuit of

  control 18 via the signal line 18 b.

  The lines 16a, 16b, 16c and 16e of signals fall or pass at the logic level "O", and the AGC circuit 12 stops working. Next, the AGC circuit 12 maintains, for a time interval corresponding to the reception. -

  the information of a line, the amplification factor

  cation which is determined immediately before the detection

synchronization signal.

  When the next 8-bit image signal is received, the signal line 48a of the counter 48 goes to logic level "1", as indicated at 55 on the line k of FIG. 5 Since the output 50 has the OR gate 50 is at logic level "1" at this instant, the signal line 16 c of the D-type flip-flop 58 goes to logic level "1", as indicated at 56 on line 2 of FIG. synchronism with the pulse of the following bit synchronization clock Although the lines

  16a and 16b of signals are both logically

  that "O" at this moment, the signal line 16 d is at the level corresponding to that of the signal line 16 b

  at the instant indicated in 54 at line 2 of FIG.

  Thus, the line 16 d is at the logic level "1", indicating that the guardband signal is received. The control circuit 18 does not store any information in the double buffer memory 26. As previously mentioned, the signal

  guard tape is intended to eliminate any harmful effect

  side edge of a sync signal

  On the next image signal Since the synchronization and jump signals have a high level, the phenomenon of fringe or over-modulation also has a large amplitude. The effect of the introduction of a guardband signal is important.

  The reception of the next signal is triggered.

  As indicated at 57 on line d of FIG. 5, a high level signal is detected. When the high level is maintained for a duration of 384 ps, flip-flop 42 of type D is positioned as indicated at 58 on line h of FIG. Figure 5 When the signal level of black or a

  black dot is then detected, as indicated in 59 in the.

  line e of FIG. 5, the flip-flop 44 of the D type is posi-

  and the line 16 d goes to logic level "1", as indicated at 510 on line j of FIG. 10. Output 50 a of OR gate 50 then goes to logic level "1". When signal line 48 goes to logic level "1" at the instant of the next byte, ie as indicated in Sll at line k of the

  5, signal line 54a, connected to the end of FIG.

  The input unit of the D-type flip-flop 58 goes to logic level "1" via the AND gate 52 of FIG.

  OR gate 54 Therefore, the latch 58 is position-

  born by the next bit synchronization clock pulse arriving via line 22a,

  and line 16c goes to logic level "1", as indicated

  512 to the line L of FIG. 5 Since the lines 16a, 16b and 16d of signals are respectively at the logic levels O "," 1 "and" O ", the received signal is discriminated as being In this case, the control circuit 18 is intended to write a block of the white signal, that is to say the data of 64 bits of the signal.

  In a similar way, a jumping signal cor-

  corresponding to the second block and a guardband signal are detected at times indicated at 513 and 514, respectively, at line ú of Figure 5 A signal

  image corresponding to the third block is then received.

  The first image transmission method was therefore

  described When the condition of the line or the characteristics

  circuits are bad during a transmission

  performed in accordance with the first method of

  image mission described above, the receiver is subject to various errors One of these errors is the detection of a jump signal, from the transmitter, as an image signal (this error being designated below Terror signal jump signal); another error is the detection of an image signal from the transmitter as a jump signal (this error being referred to hereinafter as "image signal error - + jump signal"); another error is the impossibility of receiving a jump signal from the transmitter, at an appropriate time, as a result of an incorrect synchronization of the level detection

  the black signal; there is also a constitutional error

  black phantom image due to overmodulation or fringe phenomenon when a jump signal is followed by an image signal, a white balance error by over-modulation, etc. Disturbance of the picture

  due to such errors will be described with reference to the

  mitigation and group delay distortion, which are two important factors affecting

  the characteristics of the line or circuit.

  An attenuation deformation means that the attenuation degree of a transmission line is not uniform in a voice band (300 Hz to 3.4 kHz).

  distortion of the image due to attenuation distortion

  Figure 6A shows a typical characteristic curve of attenuation distortion,

  and FIG. 6B shows a curve B having the characteristic

  In Figures 6 A and 6 B the frequency is

  if Adicated on the abscissa while the amplitude of the attenuation

  is indicated on the ordinate In accordance with the curve

  characteristic A shown in FIG. 6A, the attenuation

  when the frequency increases; this characteristic

  is called the feature of over-calibration.

  According to the characteristic curve B of FIG. 6B, the attenuation increases as the frequency increases;

* this characteristic is called sub-characteristic

  equalization. In the timing diagrams of FIGS. 7 and 8, the lines a represent a signal block; the lines b

  represent a distortion-free waveform by attenua-

  tion; the lines c represent a waveform having the

  characteristic curve B or sub-characteristic

  equalization shown in Figure 6B; and the lines of

  represent a waveform with the characteristic curve

  Thus, the lines c and d of FIGS. 7 and 8 show the waveform of the received signal (signal line 14 a) when the characteristic of the line is subject to FIG. attenuation distortion It is now assumed that the frequency of the main component of the synchronization signal is lower than that of the signal

of jump.

  In the case of the overreaching characteristic

  As shown in FIG. 6A, the duration of the high level signal on line 30a decreases as indicated in line

  of Figure 7 Thus, the high level signal does not occur.

  The signal line 42a therefore does not go to logic level "1" to cause the error

  jump signal -> image signal indicated previously.

  When this error appears, the image is translated to the left relative to the normal position,

  block units (64 picture elements).

  On the other hand, in the case of the under-equalization characteristic, when an image signal (comprising a black signal in a block) is received after a jump signal and a guardband signal, a black ghost image (62) appears in a black and white image due to the bangs or over-modulation effect.

  characteristic of the line is subject to a sub-

  Equalization still intense, the duration of the signal of high level on the signal line 30a increases so that the high level signal is prolonged, even for a duration greater than 384 #s after the emission of the image signal

  by the transmitter Thus, the signal line 42 is now

  At high level, generating the image signal + jump signal error In particular, an image signal having a signal configuration similar to that of the jump signal may be mistaken for a jump signal In this case , the image is translated to the right relative to the normal position in units of blocks (62 picture elements) When the transmitter sends a jump signal, there is no problem for the receiver during the

  the duration of the high level of the jump signal However,

  that the peak value becomes very large, the fall time increases so that the detection time of the level of the black signal is delayed Thus, it appears an error that the jump signal can not be

  detected in a correct position.

  Disturbance of the image by distortion

  group delay will now be described.

  group delay is due to the fact that the speed of propagation of a signal on a transmission line varies as a function of the frequency. This group delay distortion is attributed to the non-linear relationship between the frequency and the phase. 9 A shows a

  characteristic curve C corresponding to a sub-equilibrium

  FIG. 9B shows a characteristic curve D corresponding to an oversequality. In FIG. 9A and 9B, the frequency is indicated on the abscissa while FIG.

  delay time (ms) is indicated on the ordinate.

  The delay of the group delay is represented as a difference from 2100 Hz In the case of under-equalization, the group delay distortion increases in low frequency and high frequency bands.

  In the case of over-concentration, the distortion

  group delay decreases in bands of

  low frequency and high frequency.

  In Fig. 10, the line a represents a signal block; line b represents a signal waveform without group delay distortion; line c

  represents a waveform of the characteristic curve

  that C shown in Figure 9A and corresponding to an under-equalization; and the line d represents a waveform of the characteristic curve D and corresponding to

a suralisation.

  Lines c and d of FIG. 10 also represent the waveforms of a received signal (signal line 14 a) when the characteristics of the circuit are subject to group delay distortion. When the characteristics of the circuit are subject to the signal detection time (64) of the black signal is delayed, so that the jump signal can not be detected at the correct instant. Two types of image disturbances occur depending on the position of the signal. Error in a Signal Set Figures 11 and 12 are time diagrams to explain the mode of operation of the receiver in the case of

  these two types of image disturbance.

  Fig. 11 shows a case in which the jump signal can not be received in a correct position in a continuous jump signal set. When the black signal level detection time is delayed as indicated at 516 at line c of Figure 11, the lines

  16 b and 42 b of signals of FIG. 4 are at the logic level

  that "O", the output 50a of the OR gate 50 is at the logic level "O", and the signal line 16a is at the logic level "O", Therefore, the signal line 16c does not

  does not go to logical level "1" as indicated in 517 to -

  line e of FIG. 11 In the state indicated by 518 at line e of FIG. 11, lines 16c and 16b of signals are at the logic level u 1 ", while lines 16a and 16d of signals are at logical level O "Therefore, the receiver recognizes the input signal as a jump signal Thus, tet jump signals

  are recognized as constituting a jump signal.

  In this case, the image is translated to the left relative to the normal position, in units of blocks

(64 picture elements).

  Figure 12 shows a case in which a

  image signal is received after an error due to a failure

  initiates the reception of a jump signal in the correct position When the detection time of the level of the black signal is delayed as indicated at 519 in line c of FIG. 12, the lines 161b and 42b of the signals of FIG. Fig. 4 are at the logic level "O", the output 50a of the OR gate 50 is at the logic level "O" and the signal line 16a is at the logic level "O" Therefore, as indicated at 520 at the line e of Figure 12, the

  Signal line 16 c does not go to logic level "1".

  At the instant indicated at 521 at line e of FIG. 12, the lines 16c and 16d of signals are at logic level "1" and the lines 16a and 16d of signals are at the logic level "O". Therefore, the receiver recognizes the received signal as a jump signal. At the instant indicated in 522 at the line e of FIG. 12, lines 16c and 16d are at logic level "1", while lines 16a and 16b

  16 b are at the logical "O" level. Therefore, the recep-

  recognizes the received signal as a guardband signal; the start byte of the image signal is taken as a guard band signal In this case, the image is translated to the left with respect to the position

  normal, in units of bytes (8 picture elements>.

  In the case of over-concentration, as indicated

  at 66 in line d of FIG. 10, a white imbalance is caused in the black image due to the fringe effect of the leading edge of the jump signal In the case of under-equalization, as indicated at 68 at line c of Figure 10, a white imbalance is caused in the black image due to the effect of

  fringe of the back flank of the jump signal.

  In the previous description, the distortion

  by attenuation and group delay distortion

  are considered to be factors that degrade the characteristics

  However, in a real circuit, other factors must also be considered such as attenuation lag, phase matching, phase instability, frequency deviation and instantaneous failure In most cases , we must take into account, for the disturbance of the image,

  of a combination of some of these factors.

  In a conventional analogue television system

  High-speed copy, a fixed equalizer is used to prevent picture quality degradation, as described above However, the characteristics of the telephone line vary each time a line is established The amplitude of this variation can extend from the characteristic curve A to the characteristic curve B of FIGS. 6A and 6B. This is the reason why a degradation due to a variation of the characteristics of the circuit can not be totally

  prevented in a conventional analog telecom system

high speed pie.

  In a conventional analogue television system

  high-speed copying of the type described above, it is not incorporated an automatic equalization function, in order to reduce the cost of the system If the transmission

  is performed by means of a circuit with very poor

  characteristics, the quality of the image is nota-

  degraded by transmission errors.

  In a conventional analog telecom system

  redundancy suppression type (first image transmission system), when a circuit is connected to such a system, a circuit condition control signal is not used, such a signal being intended for to control the correct reception by a receiver of a redundancy suppression signal from a

  This is the reason why the receiving state

  the redundancy suppression signal can only be confirmed by confirming the disturbance of

the image of the receiver side.

  The object of the invention is to prevent the deterioration

  the quality of the received image, such as a disturbance

  image, by changing the transmission process

  of the image following a characteristic of a line.

  Another object of the invention is to allow the prediction of a disturbance or a disturbance of a

  image received before the observation of this image.

  It is another object of the invention to produce a high quality received image by choosing a method of image transmission among three methods, according to a characteristic of a line and the dimensions of an original

and a recording paper.

  The invention will be described in more detail with reference to the accompanying drawings by way of non-limiting example and in which: FIG. 1 represents the structures of a signal emitted by the first image transmission method; FIGS. 2A to 2C show the structures of a synchronization signal, a jump signal and a guardband signal; Fig. 3 is a schematic diagram of a receiver using the first image transmission method; Figure 4 is a schematic diagram of a signal discriminator 16;

  Figure 5 is a graph of the times

  explaining how the receiver operates

  for the implementation of the first transmission

image;

  Figures 6A and 6B show features

  distortion ticks by attenuation or weakening; Figures 7 and 8 are timing diagrams showing the waveforms of the signal received when

  the characteristics of the circuit provoke deformation

  by attenuation (in the first method of transmission

image;

  Figures 9A and 9B show the characteristics of

  ticks of group delay distortion; Fig. 10 is a timing chart showing the waveforms of the received signal when the circuit characteristics cause a group delay distortion (by the first image transmission method) Figs. 11 and 12 are timing diagrams. explaining the operating mode of the receiver in the case of an error that a jump signal is not received in the correct position (by the first image transmission method;

  FIGS. 13A to 13F show structures

  control signals used in accordance with the present invention; Fig. 14 is a schematic diagram of a transmitter for transmitting the control signals and used in accordance with the present invention;

  Figures 15A and 15X represent an organization

  gram of a control sequence of a control circuit 70 shown in Fig. 14; Fig. 16 is a timing diagram illustrating the operation of the control signal generator shown in Fig. 14; Fig. 17 is a simplified diagram of a control signal receiving circuit used in accordance with the present invention; Figure 18 shows the topography of a memory A 116; Figure 19 shows the topography of a memory B 118; Figs. 20A and 20B are flow charts of a control sequence of a control circuit 114 shown in Fig. 17; and Figs. 21A, 21B, and 21C show waveforms of black ghost control signals;

  FIG. 22 is a signal diagram corresponding to

  spawning to a GII process; Fig. 23 shows image information immediately before a transmission according to the third image transmission method; and Fig. 24 is a timing diagram showing waveforms of signals transmitted by the first,

  second and third image transmission methods.

  There is the first image transmission method or redundancy suppressing method in which a set of image signal of an analysis line is divided into a block composed of each of N image signals, and transmission of an image is performed by controlling the degree of image information to be transmitted according to the black and white information of the image signals in each block Although this method has the advantage of a high speed of transmission, it has the disadvantage of a disturbance of the image if the state of the circuit is

  not good Then we know a second method of trans-

  image mission in which a set of image signal or analysis line is not divided into blocks each consisting of N picture elements Thus, the degree of image information to be transmitted n is not controlled according to the black and white information in each block By cons, a Z-bit synchronization signal is first transmitted, then image signals are transmitted after modulation This second image transmission method a for disadvantage a low transmission speed, but to advantage a disturbance of the infrequent image, even if the characteristics of the

circuit are not good.

  In addition, many of the facsimile machines, characterized by high-speed analog operation, have

  GII faxes prescribed in the T-3 standard of the Recommendation.

  CCITT to allow communication with

  fax machines from other manufacturers.

  In such facsimile machines, operating in high speed analog mode and having the

  GII fax function, it is more advantageous to

  to check the state of the line and, if this state is bad, to use the third image transmission method described herein, rather than the second

  image transmission method described above.

  The third image transmission method gives a better result than the second image transmission method in the case of a line having a very low signal-to-noise ratio or a line with very large parasitic pulses. present invention, in the facsimile machine operating in high speed analog mode and assuming

  the GII function, but not the auto EQ function.

  the line characteristic is checked before the transmission of the image and the transmission method

  is changed depending on the result of the check.

  In accordance with the present invention, if

  characteristics of the circuit are such that a disturbance

  image may be due to the first method of trans-

  mission of the image, a signal of control of the state of

  circuit is issued / received to determine that the characteristics

  the circuit is not good and a disturbance

  image may occur if a transmission is attempted in accordance with the first transmission method

  In this case, the transmission is carried out according to

  to the second method of transmitting the image.

  In this way, the disturbance of the received image can be substantially reduced due to the poor characteristics of the line and any disconnection of

line can be prevented.

  In the case of an intercontinental line (long-distance transmission line), a condition of the line (in particular a spurious condition) may change over time after the establishment of the connections. 'an original must be transmitted, the control signal is sent and received before the transmission of each of the original sheets in order to check the condition of the line, and an optimal transmission method is chosen

following the result of the check.

  Preferred embodiments of the invention

  will now be described in detail.

  Figs. 13A to 13F show a structure of a control signal which checks the state of a line to determine whether an original is to be transmitted by the first image transmission method which uses

  a jump signal to control a jump of newsgroups

  mationsde blanc, or by the second image transmission method in which all the picture element signals are modulated and transmitted without jump, or by the

  third image transmission method.

  FIG. 13A shows the overall structure of the control signals. FIG. 13A shows at E a signal having a frequency of 2100 Hz, intended for the control of a PLL circuit and a AGC circuit. signal duration at the high level of 46 bits and a duration of the black signal of 5 bits, then a duration of the level of the white signal of 5 bits The same is true for six synchronization signals and ten synchronization signals shown in Figure 13 A Signal

  of jump control, shown in Figure 13A, is

  13 C, while a control signal

  black ghost image, shown in Figure 13A, is

  13E 496 jump signals, shown in FIG. 13C, each comprise a six-bit high level signal duration and a 2-bit black signal level duration. In accordance with an example of the control signal black phantom image, shown in Fig. 13E and as shown in Fig. 13F, eight signals are generated in each of which a jump signal (having a six-bit high signal duration and a 2-bit black signal) is followed by a guardband signal (having a 3-bit black signal level duration and a 5-bit blank signal level duration), a duration of the level 32-bit white signal and a duration of the signal level of

32-bit black.

  Figure 14 is a simplified diagram of a cir-

  In FIG. 14, an analyzer 67 converts an optical image information read on an original

  (not shown) in electrical image signals

  image receiver 68 receives image signals from the

  67 and generates transmission signals for use

  read according to the first-method of transmission

  image or the second image transmission method.

  A multiplexer 69 selects the signals from the image processor 68 or from a pattern generator 70 described hereinafter, and transmits the selected signals to a byte tanpon 76 which will also be described in more detail hereinafter. 67 analyzer and the 68 image processor are intended primarily-

  processing the image signals read on the original.

  The circuit for generating the circuit status control signals in accordance with the present invention

will now be described.

  As shown in FIG. 14, the byte buffer 76 serves to block a parallel 8-bit signal,

  received by a signal line 70 d, in response to an impulse

  clock pulse (byte synchronization clock pulse) received by means of a signal line 84a, and sequentially generates the blocked signal in units

  bits in response to a sync clock pulse.

  Bit reception 76 received via a signal line 74a The byte buffer 76 comprises a parallel input / serial output or other shift register and serially transmits the 8 bit signal into the order of the low order bit to the weight bit

strong -

  The gain of a variable gain amplifier 78 is changed according to the logic level of a signal line 82a. If the line 82a is at logic level "1", the gain is 2 If line 82a is at logical level "O",

  the gain is 1 The amplified signal coming out of the amplifier

  The indicator 78 is produced on a signal line 78a.

  A modulator 80, of the AM-PM-VSB type and of

  known configuration, will now be described in more detail.

  In the modulator 80, the signal received through line 78a is held in a band limited by a suitable low-pass filter so that it is possible to eliminate the undesirable parasitic tear, the signal is then modulated in At PM-VSB and it is transmitted via a network control unit

(NCU, not shown).

  A pulse generation circuit 74 of

  synchronization generates two types of sync pulses.

  In a transmitter, a bit synchronization clock pulse having a frequency of 7740 Hz, for example, appears on the signal line 74a and is applied to the byte buffer 76 and a delay element 82. given that the transmission data are transmitted in response to this bit rate data, the transmission speed is

  7740 bits per second A sync clock pulse

  The multiplication of bytes, obtained by division by 8 of the frequency of the bit synchronization clock pulses, appears on the signal line 74 b and is applied to the target generator 70, a control circuit 72 and a control element. delay 84 The byte synchronization clock pulses have a frequency of

7740/8 = 967.5 Hz.

  The delay element 82 includes a latch or other It delays the signal received by a line 70 b of

  signal of a duration corresponding to a period of

  bit synchronization clock received via line 74a The delayed signal is

  produced on a signal line 82a.

  The delay element 84 serves to produce, on a

  signal line 84a, a sync clock pulse

  which is obtained by delaying the byte timing clock pulses from the timing pulse generating circuit 74 and received via the signal line 74 b, the timing being one period of time. predetermined time (corresponding to half the period of the bit synchronization clock pulses from the timing pulse generation circuit 74) The delayed clock pulse is used as a pulse to block the signal at the same time.

  8 parallel bits in the byte buffer 76.

  The pattern generator 70 includes a 10 x 124 bit read-only memory and an address indicator. Table 2 shows the topography of the target generator memory. 10-bit data is generated.

  to correspond to each of O to 123 addresses.

  The 10-bit data is generated on the signal line 70 q, the ninth bit data from the least significant bit is generated on the signal line 70 b and the least significant bit applied to the 8 th data. bit

  is produced on a 70-line signal.

TABLE 2

  Address Data Signal Address Data Output output signal Synchronization signal Synchronization signal Synchronization signal Synchronization signal Synchronization signal Synchronization signal Synchronization signal Synchronization signal Synchronization signal Synchronization timing 13 FH 1 FFH 13 FH 1 FFH 13 FH 1 FFH 13 FH IFFH 13 FH 1 FFH 13 FH 1 FFH 13 FH

OF 8 H

  33 FH 1 FFH 13 FH 1 FFH 13 FH Synchronization signal Synchronization signal Synchronization signal Synchronization signal Synchronization signal Synchronization signal Jump signal 496 Synchronization signal Synchronization signal t 1 FFH 13 FH 1 FFH 13 FH 1 FFH 13 Fa 1 FFH 13 FH 1 FFH 13 FH 1 FFH 13 FH 1 FFH 13 FH 1 FFH 13 FH 1 FFE 13 FH 1 FFH Address Data Signal Address Data Output output signal Synchronization signal Jump signal 496 Synchronization signal Synchronization signal Synchronization signal Jump signal 496 Synchronization signal Synchronization signal Synchronization signal 33 FH 1 FFH 13 FH 1 FH 13 FH 1 FH 13 FH 1 FH 13 FH 1 FH 13 FH 1 FH 13 FH

0 F 8 H

13 FH

OF 8 H

  OFFH OOOH 13 FH Jump signal 496 Synchronization signal Synchronization signal

Signal of -

  synchronization Synchronization signal Synchronization signal Synchronization signal Black ghost image control 1 FFH 13 FH

OF 8 H

  33 FH l FFH 13 FH 1 FFH 13 FH l FFH 13 FH

OF 8 H

  33 FH 1 FH 13 FH 1 FH 13 FH 1 FH 13 FH

OF 8 H

  Address Data Signal Address Data Output Signal _ Output Black Ghost Image Control Black Ghost Image Control Black Ghost Image Control Image Control

black ghost -

  black ghost control 13 FH

OF 8 H

OFFH OOOH 13 FH

OF 8 H

  OFFH OOOH 1 FFH 13 FH 1 FH 13 FH 1 FH 13 FH 1 FH 13 FH 1 FH 13 FH 1 FFH black ghost control J black ghost control Synchronization signal Synchronization signal Synchronization signal Synchronization signal Signal Synchronization signal 9 Q

OF 8 H

OFFH OOOH 13 FH

OF 8 H

OFFH OOOH 13 FH

OF 8 H

OFFH OOOH 13 FH

OF 8 H

OFFH OOOH 13 FH

OF 8 H

  OFFH OOOH Address Data Signal Address Data Output output signal 114 13 FH 6 119 l FFH Signal from l To synchronization 1 FFH Signal from 120 13 FH 9 synchronization 116 13 FH 7 121 1 FFH Synchronization signal 117 1 FFH Signal from 122 13 FH 10 synchronization

118 13 FH 8 123 OF 8 H

  The 8-bit information gain that is

  in the byte buffer 76 via the signal lines 70a and 70d and which is sequentially generated in response to bit synchronization clock pulses is determined according to the signal present on the line 70b. signal present on the line 70b is applied to the amplifier 78 to gain

  variable via the delay element 82.

  The circuit condition control signals are transmitted by setting the address indicator to 0 and by producing, on the lines 70a, 70b and 70c of signals, current address data. the address indicator each time it receives a byte synchronization clock pulse via line 74 b The address indicator progresses on reception

  pulses from the control circuit 72.

  When a pulse is generated on a signal line a, the address indicator is incremented by one. The address indicator is set to O

in the initial state.

  As indicated previously, the circuit 72 com

  command the address indicator of the generator 70 of the target.

  We will now describe an example in which the command

  a sequence is performed by means of a microproces-

  In the initial state, the address indicator of the gen-

  The controller 70 is set to O and the contents of register B are set to 1 in accordance with the main control operation of control circuit 72, when a byte sync clock pulse is generated on line 74b. signal, the signal present on line 70c is received in order to introduce the data of

  the current address, indicated by the address indicator.

  It should be noted that the data input via the signal line 70c is such that a 10-bit output signal can be generated by the previously indicated read-only memory Using the data received via the In line 70c, the control circuit 3.5 establishes the control of the period of maintenance of the address indicator, in accordance with which the same data are produced on the signal lines 70a and 70b of the generator 70. in response to receiving other synchronizing clock pulses

multiplet.

  The control sequence followed by the control circuit 72 is shown in Figs. 15A and 15B. In step 85 shown in Fig. 15A, initialization is performed; the digit 1 is entered in the register B In step 86, it is determined whether a pulse is generated on the signal line 74 b, that is to say if a pulse

  byte synchronization clock is generated.

  If the answer in step 86 is yes, the contents of register B are decremented by 1 in step 88.

  then, in step 90, if the contents of register B are 0.

  If the answer is no to the interrogation of step 90, then, in step 91, it is determined whether the contents of the

  register B is 1 If the answer is yes to the question

  In step 91, a pulse is generated on the signal line 72a to advance the address indicator in step 92. If the answer is yes to the interrogation of step 90, the signal is applied on line 70c during step 74; the address data currently indicated by the address indicator is introduced In step 96, it is determined whether the input data present on the line 70c is 1 FFH If the answer is yes to the interrogation of the step 96, the value 5 is entered in the register B during the step 106 On the other hand, if the answer is no to the interrogation of the step 96, it is determined, at the step 98, whether the data item d present on the line 70c is OFFH If the answer is yes to the interrogation of the step 98, the value 4 is introduced in the register B during the step 112 If the answer is no to the interrogation of step 98 and if the answer is yes to the interrogation of step 102 or step 104, the value 1 is entered in register B

  in step 110 In step 111, a pulse is generically

The signal line 72a is set to advance the address indicator by 1. If the answer is no to all the interrogations of steps 96 to 104, the value 4 is entered in step 112.

  A case will now be described in which the indi-

  The address determination is set to 0 and a synchronization signal is transmitted. The determination made in step 86 is repeated until a pulse is generated on the signal line 74b. When the pulse is finally generated on the line 74b and that the answer is yes to the interrogation of the step 86, the contents of the register B is reduced from 1 to O during the step 88 Therefore, the answer yes is obtained to the interrogation of step 90 When the data is applied to the signal line 70 c in step 94, it presents itself

  in the form 1 FFH At this time, a logic level signal

  that "1" is produced on line 70b and a "FFH" signal (8-bit high level signal) is produced on the line

  70 b by the generator 70 of sight Since the data

  present on the signal line is 1 FFH, the answer yes is obtained at the interrogation of step 96 and the value 5 is entered in register B during step

  106 When the second synchronization clock pulse

  byte is generated, the contents of register B are changed to take the value 4 Then the

  the contents of register B is reduced to 3 during the general

  third synchronization clock pulse

  bytes, then at 2 when generating the fourth byte synchronization clock pulse, and at 1 when generating the fifth byte synchronization clock pulse <"1"

  is produced on signal line 70b and "FFH" is pro-

  duit on signal line 70a during generation

  second-fifth synchronous clock pulses

  By this time, the answer yes to the interrogation of step 91 is obtained and the address indicator is advanced to 1 in step 92. When another synchronization clock pulse of bytes is generated, the contents of the register B is 0 and the answer is yes to the interrogation of the step 90 When the data is applied to the signal line 70 c in the step 94, the data present on the line 70 c is 13 FH At this moment, a "1" is produced on line 70b and "3 FH" is

  produced on the line 70a by the target generator 70.

  Since the data present on line 70c is 13FH, yes is obtained in response to the interrogation of step 102, and 1 is entered in register B at step 110. The address indicator is advanced from 1 to 2

  in step 111 A signal, which is emitted when the in-

  address indicator goes from 0 to 1, is considered; the data 1 FFH is transmitted five times and the data 13 FH is then transmitted once Since the ninth bit from the least significant bit is "1" in each case, a high level signal is transmitted. 8 bit information is transmitted sequentially from the least significant bit by the byte buffer 76, 46 bits of the high level signal and 2 bits of the black signal are sequentially transmitted. This corresponds to a synchronization signal as shown in FIG. Figure 13 B Then, all the control signals are emitted on the circuit, in a similar way to that

previously described.

  Fig. 16 is a timing diagram showing signals generated by the signal generating circuit

  control; two synchronization signals are transmitted.

  The signal appearing on line 78a of the signal of the

  variable gain controller 78 is a transmitted baseband signal having the waveform shown at line a of FIG. 16 In the initial state, the indicator

  address is set to O (line f of Figure 16).

  In response to a byte synchronization clock pulse K 1 on line 74b, shown at line c of FIG. 16, "FFH" is produced on line 70a and "1" is produced on line 70 b Thus, the content of the byte buffer 76 is FFH, as shown in line d of the

  FIG. 16, while the gain control signal

  a logic level "1", as shown in line e of FIG. 16 Thus, a logic level 8 bit signal 1 "is produced as a transmission bit signal (signal line 76a), as shown in FIG. line b of Fig. 16, and a high-level 8-bit signal is produced as an output signal of the amplifier (signal line 78a), as shown in line a of Fig. 16 The same operation as that performed during

  receiving the clock pulse Kl of synchronization

  multiplet is performed for each pulse

  clock K 2, K 3, K 4 and K 5 multiplet synchronization.

  When a clock pulse K 5 is generated on the line 74b, the address indicator changes from 0 to 1 When the next clock pulse K 6 is generated, 3 FH is produced on the line 70a , while the value 1 is produced on the line 70b As indicated in the line b of FIG. 16, the content of the byte buffer 76 becomes equal to 3 FH, while the gain control signal goes to the logic level. O ', as indicated in the line e of the Igure 16 Thus, it is generated, as a signal

  binary transmission (signal line 76a), as indicated

  that at line b of FIG. 16, a logic level 6 bit signal "1" and a logic level 2 bit signal "O". As shown in line a of FIG. 16, it is generated as a signal output of the amplifier (signal line 78a), a 6-bit high level signal

  and a 2-bit black level signal When the impulse

  Byte synchronization clock pulse K 6 is generated on the signal line 74 b, the address indicator changes from 1 to 2 The same operation as that performed on reception of the clock pulses K 1, K 2, K 3, K 4 and K 5

  the multiplet synchronization is carried out at the

  When the clock pulse K11 is generated on the line 74b, the address indicator changes from 2 to 3 times the clock pulses K 7, K 8, K 9, K 10 and K 1 L When the clock pulse K 12 is generated on the line 74 b, the same operation as that performed on the reception of the clock pulse K 6 is executed. In addition, control signals are

  products on the circuit, in a similar way.

  The mode of operation for generating the circuit condition control signals used in the present invention will now be described in greater detail.

detail.

  Figure 17 is a simplified diagram of a cir-

  baked generation of state control signals from

  circuit, which is substantially identical to that

  3, the circuit shown in FIG. 17 differs from that shown in FIG.

  that the printer 20 and the buffer memory 26 are sup-

  and a control circuit 114, a memory A 116, and a memory B 118 are added in the case of the circuit shown in FIG. 17. The memory A 116 is

a RAM of 8 x 7 bits.

  Figure 18 shows the topography of memory A 116 As shown in Figure 18, memory A 116 includes 1 byte memory areas for CNTSY 1 (sync count), CNTPIX (picture element count), CNTGRD (custody account), CNTSY 2 (sync account), and CHKPTR (indicator control); and a 2 byte memory area for CNTSKP (hop count) These memory areas, respectively, count the sync signals, the image signals (pix), the guardband signals, and

jump signals (jump).

  The memory B 118 is a random access memory of 8 x 100 bits or others. FIG. 19 shows the topography of the memory B 118. As shown in FIG. 19, the memory B 118 has memory addresses.

from 0 to 99.

  The control circuit 114 receives the signals

  generated by the issuer, and memorizes the results

  states of the reception of the jump control signal in the memory A and the result of the reception of the black ghost control signal in the memory B. As in the case of the control circuit 18 shown in FIG. , the control circuit 114 produces an erase pulse on a signal line 114c at the reception of the data for the discrimination of the synchronization signal, the jump signal, the signal

  guard tape and the image signal from the

  criminator 16 of signals via the lines

  16a, 16b, 16c and 16d In response to this impulse

  In the initial state, the control circuit 114 assumes the control of the memories A 116 and B 118. The control circuit 114 assumes the control of the memories A 116 and B 118. sets the contents of the memory areas CNTSYI, -CNTPIX, CNTGRD, CNTSKP, CNTSY 2, and CHKPTR of memory A 116 to -28, 0, -4, -1984, -7, and 0); and it also positions the contents of the 8 x 100 bits of the memory B 118 to FFH (8-bit high level signal) The control circuit 114 acknowledges receipt of one of the synchronization, jump, and guardband signals and picture when line 16c of

  signal changes from logic level "O" to logic level "l".

  When line 16c goes to logic level "1", the cir-

  control bake 114 supports the levels of the signal lines 16a, 16b and 16d in order to discriminate among the following cases: 1) receiving a synchronization signal (the signal line 16a goes to logic level "1" in this case); 2) reception of a jump signal (signal line 16a is at logic level "O" and line 16b is at logic level "1"); 3) receiving a guardband signal (signal lines 16a and 16b are at logic level "O" and line 16d is at logic level "1"); and 4) receiving an image signal

  (lines 16a, 16b and 16d are at logic level "0").

  If the synchronization signal is received, the contents of the memory area CNTSY 1 are incremented by 1 If the jump signal is received, the contents of the memory area CNTSKP is incremented by 1 If the guardband signal is received , the contents of the memory area CNTGRD is incremented by 1 If the image signal is received, the

  contents of the CNTPIX memory area is incremented by 1.

  The contents of the memory areas CNTSY 1, CNTSKP, CNTGRD and CNTPIX can be respectively incremented by 1 by the extraction of the current contents, via a signal line 116 A, and production of results incremented via signal line 114a This operation is performed while the contents of the memory area CNTSY 1 are negative when

  the contents of the memory area CNTSY 1 is no longer nega-

  tif, the next command cycle is executed.

  When line 16c goes to logic level "1",

  the signal on line 16a is extracted to determine

  if a synchronization signal or a jump signal is received If a synchronization signal is received, the

  contents of the memory area CNTSY 2 is incremented by 1.

  If a signal other than the synchronization signal is received, the data produced on the line 24a is placed in the memory B The memory B 118 is addressed by the contents of the memory area CHKPTR in this case When the synchronization signal is received, after the data has been placed in the memory B 118, the contents of the zone

  CHKPTR is incremented by 1 The previous operation

  dente is performed if the contents of the memory area CNTSY 2 is negative The reception of the control signals is completed when the contents of the memory area

CNTSY 2 is no longer negative.

  Figures 20A and 20B show the flowchart

  followed by the control circuit 114 described above.

  In step 120, it is determined whether the signal line 16 c is at logic level "1", i.e. if a signal discrimination operation is completed. If the answer is YES to the interrogation of step 120, it is then determined in step 122 whether the signal line 16a is

  at logical level "1", ie if a signal of syn-

  chronization is received If the answer is YES to the question

  In step 122, the contents of the memory area CNTSY 1 is incremented by 1 in step 124. It is then determined in step 126 whether the contents of the memory area CNTSY 1 are negative. i.e., if the reception of the jump signal is completed. If the answer is NO to the interrogation of step 126, the program jumps to the top of the represented flowchart.

  in Fig. 20B, at step 128 to execute the reception

  If the answer is YES to the interrogation of the step 126, the program returns to the step 120 If, during the step 122,

  signal line 16a is at the logical level "O", that is,

  i.e., if the synchronization signal is not received, it is then determined, in step 130, whether the signal line 16 b is at logic level "1", i.e.

  jump signal is received If the answer is YES to the inter-

  In step 130, the contents of the memory area CNTSKP is incremented by 1 in step 132, then the program returns to step 120. However, if the answer is NO to the interrogation of step 130, that is, if the jump signal is not received, it is determined in step 134 whether the signal line 16 d is at logic level "1", that is, say if a guardband signal is received If the answer is YES to the interrogation of step 134, the contents of the memory area CNTGRD is incremented by 1 in step 136 and the program returns to the step 120 If the answer is NO to the interrogation of step 134, i.e. if the image signal is received, the contents of the CNTPIX memory area is incremented by 1 at step 138 and the program then returns to step 120 The above operation is repeated until the contents of the memory area CNTSY 1 are no longer negative The contents of the memory area CNTS Y 1 is no longer negative, that is, it is

  zero after receiving 28 synchronization signals.

  The control signals have the structures shown in Figs. 13A to 13F. After receiving a signal with a frequency of 2100 Hz, 16 synchronization signals are received. During the next reception of the jump signal, 9 signals are received. six sync signals are received between the jump control signal and the black ghost control signal When 3 sync signals are received between the jump control signal and the black ghost image signal, the contents of the memory area CNTSY 1 becomes equal to zero When the contents of the area of

  memory CNTSYI becomes equal to zero, the commu-

  In this example, the jump control signal is received under the control of the program shown in FIG. 20A. The result of the reception is placed in memory A 116. The signal is passed to the upper part of the flowchart shown in FIG. Black phantom image control is received under the control of the program shown in Fig. 20 B and the result of the reception is placed in the memory B 118. If the control signals are correctly received, the contents of all the zones of

  CNTSY 1, CNTSKP, CNTGRD, and CNTPIX are zero.

  This means that 1984 jump signals, 4 guardband signals, and no image signals are received during the

  reception of 28 synchronization signals.

  The flowchart shown in FIG. 20B will now be described. In step 140 of FIG. 20B, it is determined whether the signal line 16c is at logic level "1", i.e. a discrimination operation

  signals is completed If the answer is YES to the interroga-

  In step 140, it is then determined, in step 142, whether the signal line 16a is at logic "1", i.e. if a synchronization signal is received. answer is YES to the interrogation of step 142, the contents of the memory area CNTSY 2 is incremented by 1 in step 144 It is determined, in step 146, if the contents of the memory area CNTSY 2 is negative, that is to say if the reception of the control signals is completed If the reception of the control signals is not yet complete or if the answer is YES to the interrogation of step 146, the program

  returns to step 140 If the answer is NO to the question

  In step 146, a determination of the end of the reception of the black ghost control signal is performed at step 148. This determination is made by counting the number of black dots in the black and white data. to three bytes following the guardband signal If reception is normal, no black spots are detected If signal line 16a is at logic level "O" or if the answer is NO to the interrogation of step 142, that is to say if the synchronization signal is not received, the data produced on the signal line 24 a is placed in the memory B. This is addressed by the content of the zone of memory CHKPTR At step 152, the contents of the zone

  memory CHKPTR is incremented by 1.

  In this way, the reception of the signals of

  control transmitted by the transmitter ends.

2525057.

  The second image transmission method will now be briefly described The following modification

  is made to the first image transmission method.

  In the facsimile transmitter, an analysis line of a sequence of picture element signals is not divided into blocks each comprising the predetermined number (N) of picture element signals; that is, the amount of transmitted image is not controlled according to the information of white and black, but all the picture element signals are modulated and emitted Since these signals are not not divided into blocks, no jump signal is transmitted In the facsimile receiver, the control circuit 18 of FIG. 3 does not receive the signal 16b from the signal discrimination circuit 16, but it discriminates between the synchronization signal, the guard signal or the image signal, as indicated in Table 3 relating to the first signal discrimination. The delay circuit 56 of FIG. 4 receives the signal 16 a instead of the signal 16 b. than the fax sender

  does not emit the jump signal, the latter is not

crimine.

Table 3

  One of the causes of an error in which the receiver considers the jump signal from the transmitter as an image signal is the short duration of a high level, i.e. may be that the structure of the jump signal is slightly modified (eg the duration of the high level is doubled) and that this signal is transmitted, rather than a switching is performed from the first method of 16 c 16 to 16 d Signal 1 1 x synchronization signal 1 O 1 guard signal 1 OO image signal image transmission to the second method when it is not possible to transmit the original by the first method. The third method of image transmission will now be described. This third method uses the image transmission mode used in the facsimile apparatus GII, defined by the CCITT recommendation T 3.

  The difference lies in the phase agreement and the

  density of secondary analysis lines.

  The phase agreement will be explained first Figure 22 illustrates an operation performed in a device

  GII fax, defined by CCITT Recommendation T 3.

  In Fig. 22, reference numeral 154 designates an equipment identification signal CED which is called

  indicates that the called equipment is a non-sound terminal.

  Reference numeral 156 designates a signal GI 2 of identification

  GII which indicates that the equipment is ready to receive information from an original and can receive at least one sheet of an A 4

  work information station, through the transmission system

  recommended mission to the fax apparatus GII The reference numeral 158 designates a GII command GC 2 signal which indicates that the transmitter is the recommended transmission system to the GII apparatus. The reference numeral 160 designates a control signal LCS of transmission line whose function is to enable the receiver to equalize the transmission line This signal is optional The reference numeral 162 designates a phase signal PHS

  intended for the tuning of the transmitter and receiver phases.

  Reference numeral 164 designates a CFR 2 signal ready for reception which indicates that the receiver has completed the phase agreement and is ready to receive the image

  of the original The reference number 166 designates an informa-

picture image of the original.

  As shown in FIG. 22, the facsimile apparatus GII defined by CCITT recommendation T 3 assigns the transmitter and receiver phases by means of the

  phase PHS signal from the transmitter.

  In the third image transmission method, the phase tuning is not performed in the process flow, but immediately before the transmission of the image information If the transmission of the original by the third method image transmission is decided in the prerequisite process including the control of the state of the line, it is not necessary to emit the PHS signal for 6 seconds for phase synchronization, since the remaining fax machines grant

  the phases in a non-mechanical, but electric way.

  Figure 23 shows a signal such as

  immediately before issuing information

  image by the third image transmission method.

  In FIG. 23, the reference numeral 168 designates a signal of 2100 Hz emitted for setting an automatic gain control circuit and a phase-locked closed circuit of the receiver. The reference numeral 170 denotes

  a phase signal intended to match the phases of the transmission

  The reference numeral 172 designates a 2100 Hz signal emitted to allow the receiver time to change from the phase signal reception mode.

  the mode of receiving the image information The reference

  Digital reference 174 designates an image signal of the original.

  As shown in FIG. 23, in the third image transmission method, the transmitter and receiver phases are tuned by the phase signal.

  transmitted immediately before the transmission of the information

image.

  The determination of the density of secondary analysis lines will now be explained In the facsimile apparatus GII defined by the CCITT T 3 reconrandation, the density

  of secondary analysis lines is 3.85 lines / mm.

  In the third image transmission method, if

  the mode displayed on the panel is the normal mode, the den-

  the secondary mode is set to 3.85 lines / mm, and if the mode displayed on the panel is the fine mode, this density is set to 7.7 lines / mm. 7.7 lines / mm can be easily obtained by decreasing the paper feed speeds established by a step motor of a reading unit and by a step motor of a recording unit, so that these speeds are equal to half of those used for the secondary scan line density of 3.85 lines / mm. The third image transmission method is advantageous because

  phase is achieved more rapidly than by means of

  GII and fine mode can be used.

  The mode of reception of the control signal transmitted by the transmitter, the second image transmission method and the third image transmission method have been described on the basis of the result of the reception of the control signal transmitted by the transmitter. transmitter, it is determined whether the image of the original is to be transmitted by the first image transmission method, by the second image transmission method or by the third image transmission method The fact that it is necessary to transmitting the image of the original by the second method or by the third method is determined from the size of the sheet of the original loaded into the emitter and the size of the recording paper loaded into the receiver. The first, second or third image transmission method is determined from the result of the reception of the control signal, in accordance with the

table 4.

Table 4

  Control signal Black phantom control signal jumping signal First picture transmission method Second ox image transmission method or xo third image transmission method xx In the case of the jump control signal and of the black ghost control signal, the states

  o (good) and x (bad) are determined.

  As shown in Table 4, if the results of the determination for the jump control signal and the black ghost control signal are o, the image of the original is transmitted by the first method, and if at least one of the results associated with the jump control signal and the black ghost control signal is x, the image of the original is transmitted

  by the second method or by the third method.

  A jump control signal is a signal for primarily detecting the image signal jump signal error and an error in which a jump signal is not received in the correct position due to a black dot delay, when the image of the original

  is emitted by the first image transmission method.

  Discrimination between two alternatives o or x is performed for the jump control signal. The discrimination algorithm will now be described where indicates a reproduction of 496 x 4 jump signals; the content of the memory area CNTSKP of the memory A 116 is zero x indicates the non-reproduction of 496 x 4 jump signals; the contents of the memory area CNTSKP of memory A 116

is not zero.

  A black ghost control signal

  is a signal intended primarily to detect the general

  black ghost image in a white image by fringe effect when the image of the original is

  transmitted by the first image transmission method.

  If the circuit exhibits the characteristic curve B, i.e., an undersequality, a jump signal image signal error can also occur. This error is always accompanied by the black ghost image

  in a white image by fringe effect

  nation between two alternatives o and x is performed for a black ghost control signal, as previously described Figs. 21A to 21C show a portion of a black ghost control signal A control signal of black ghost image actually comprises 8 signals as shown in Figs. 21A-21C. Fig. 21A shows a baseband signal transmitted, while Figs. 21B and 21C show received baseband signals As indicated in P1 in FIG. 21B and P 2 in FIG. 21C, it is controlled how many black dots are generated during the duration of a white signal level of three multiplets FIG. 21B shows a case in which no point black is generated during the duration of the level of a three byte white signal and FIG. 21C shows a case in which a black dot is generated during the duration of the level of a three byte white signal, such as indicated in P 3 Since the signal shown in FIGS. 21A to 21C is

  generated 8 times as a fan image control signal

  black dome, we check how many black dots are generated during the duration of 3 x 8 = 24 bytes

the level of the white signal.

  If at least one of the checks results for the skip control signal or the ghost control signal noime is x as a result of the transmission and reception of the line control signal, the image of the original is transmitted either by the second image transmission method or by the third method,

  the process being determined in the following manner.

  The image of the original is transmitted in the second image transmission method only when the format of the original placed in the transmitter is B 4 and the format of the recording paper placed in the receiver

is B 4.

  When the format of the original placed in

  the transmitter is A 4 and that the recording paper size is

  placed in the receiver is B 4, when the format of the original placed in the transmitter is A 4 and the format of the recording paper placed in the receiver is B 4, and when the format of the original placed in the transmitter is B 4 and the format of the recording paper placed in the receiver is A 4, the image of the original is

  transmitted by the third method.

  Thus, the receiver receives the control signal transmitted by the transmitter and determines whether to transmit the image of the original by the first image transmission method, or by one or the other of the

  second and third image transmission methods.

  The choice of one of the three image transmission methods must be made before the transmission of the image

  of the original, that is to say during the preliminary process

  This preliminary process is carried out by the use of an acoustic signal not defined in the recommendation

CCITT T 30.

  If the control indicates that the state of the line is bad, the second image transmission method is chosen when the format of the original placed in

  the transmitter is B 4 and the format of the recording paper

  In the embodiment described, the third image transmission method uses the image transmission method in the facsimile apparatus GII, defined by the CCITT recommendation T 3. the original placed in

  the transmitter is B 4 and the format of the recording paper

  When placed in the receiver is B 4, the following mode can be used by changing the transmit and receive clocks of the image information. In other words, if the state of the line is bad, the third method

image transmission is chosen.

  Fig. 24 shows waveforms as they occur when the image signal is emitted

  in the first, second and third

  image mission Line (a) in Figure 24 shows a

  general of imaae to &put; the creeper (b) of Fig. 24 shows a waveform which appears when the image signal is emitted in the first image transmission method line (c) of Fig. 24 shows a waveform which appears when the image signal is emitted by the second ip transmission method; and line (d) of Fig. 24 shows a waveform that appears when the image signal

  is emitted by the third image transmission method.

  A comparison of the lines (c) and (d) of Figure 24 shows that the level of the image signal of the line (d) is twice as high as that appearing in the line (c). Thus, in the case of a line having a very low signal / noise ratio, the third image transmission method is more advantageous than the second method. Since the second method of imaae transmission is of the synchronization type, transmission, it is more affected by spurious pulses appearing between the synchronization signals than the third image transmission method which is of the independent synchronization type. As described previously, the third image transmission method uses the GII function. It is therefore effective only for the recording in A 4 format. It is possible to modify the circuits to allow

  the full-size transmission in the B 4 format in the third

  However, the full-size transmission in the B 4 format is performed by the second image transmission method. The present invention is therefore suitable for the case in which the high-speed analog transmission is

  selected in the facsimile machine having the characteristic

  high-speed analog operation and the GII function Even if this unit is not equipped with the automatic equalization function,

  the characteristic of the line is checked before the transmission

  Image mission and transmission method is chosen according to the result of the verification so that the degradation of the quality of the image received as a result of a bad characteristic of the line can be significantly reduced compared to analog devices

  earlier operating at high speed.

  As described above, according to the invention, there is provided a high speed analog facsimile apparatus in which the state of the line is checked before

  image transmission and an optimal method of transmitting

  The image mission is chosen according to the result of the verification, this apparatus being easy to implement by a user. In particular, one of the following image transmission methods is chosen for the transmission of the image. an original: (1) the first image transmission method in which a line of analysis of a sequence of picture element signals is divided into blocks each consisting of N picture element signals and the transmission of the image is quantitatively controlled according to the white and black information of the picture element signals in each block more particularly; the

  t-bit synchronization signal is transmitted before the

  each image analysis line and, if the block contains black information (first block), N image signals are modulated and transmitted, and if the block contains all blank information (second block). ), the N-bit jump signal (n <N) is modulated and transmitted, and if the block immediately preceding the first block to be transmitted is the second block, the m-bit guard signal is modulated and transmitted; (2) the second image transmission method in which an analysis line of a picture element signal sequence is not divided into blocks, each of which consists of N picture element signals; that is to say, the

  transmission of an image is not ordered quantitatively

  by the black-and-white information, but the t-bit sync signal is transmitted prior to the transmission of the pixel signals of each scan line, and then all the pixel signals are modulated and emitted; (3) the third image transmission method which uses the image transmission method implemented in the facsimile apparatus GII, defined in the CCITT recommendation T 3 (although the phase agreement and the determination of the density of lines of analysis

secondary are different).

  The state of the line is verified by the transmission and reception of the control signal, and if it is determined that the first image transmission method causes deformation of the image, the second or the

  third image transmission method is selected

  the format of the original placed in the transmitter and the format of the recording paper placed in the

  receiver The image transmission system according to the

  verntion avoids any deterioration of the image In summary,

  the possibility of adapting the analogue fax machine

  high speed in the bad state of the line

  significantly improved in the case of an international line

  continental (long-distance line), the state of the line (especially in the case of spurious pulses)

  changes over time after the line has been connected.

  Therefore, when a multi-sheet original has to be transmitted, the control signal is sent and received before the transmission of each original, so that the condition of the line is checked so that the optimal method of transmission is chosen to each time

  function of the result of the verification.

  It goes without saying that many modifications can be made to the apparatus described and shown

  without departing from the scope of the invention.

Claims (7)

  A facsimile apparatus, characterized in that it comprises means for transmitting and receiving a control signal having a predetermined image configuration before the transmission of image information read on an original, and means ( 114) for selecting, after verifying the state of a line by said control signal, one of a plurality of methods, namely a first image transmission method in which a jump signal requesting a jump is transmitted and received in accordance with blank information read from the original, a second image transmission method in which said jump signal is not transmitted, and a third image transmission method in which a phase chord is carried out immediately before   the transmission of image information.   Faxing apparatus according to claim 1, characterized in that the first image transmission method divides an analysis line of a signal sequence.   of pixels read on said original in blocks   each with N picture element signals, and   the amount of information transmitted as a function of   formation of white or black contained in the signals   of pixels in each block, the second and third   second image transmission method that does not divide an analysis line of a sequence of picture element signals read on said block original: each comprising N picture element signals and not controlling the   amount of information transmitted but modulating and trans-   setting all white and black picture element signals of the analysis line, said control means selecting said second image transmission method, wherein the level of the white picture element signal is lower than the high level of a synchronization signal when both said original placed in a transmitter and a recording paper placed in a receiver are of a first format, and selecting said third image transmission method , in which the level of the blank picture element signal   is substantially equal to the high level of the sync signal.   chronization when both said original placed in the transmitter and the recording paper placed in the receiver are of a second format.   3 Facsimile apparatus according to one of the   1 and 2, characterized in that the control signal comprises a synchronization signal, a jump control signal having a predetermined number of repetitions of an alternative combination of a jump signal and the synchronization signal, and a Black ghost image signal having a predetermined number of repetitions of a signal block consisting of the jump signal, a blank information signal and a signal information black.   Faxing apparatus, characterized in that it comprises control means (114) for receiving a control signal comprising a synchronization signal, a jump signal and a black ghost image signal before receiving a signal. an image signal read on an original, and selecting, according to a reception condition of the control signal, a mode of receiving said image signal between a first image transmission method and a second or third image transmission method, and to select, according to the format of the original and the format of a recording paper, the mode of reception of said image signal between said second image transmission method and said third image transmission method, the apparatus further comprising a first memory (A 116) for receiving said jump control signal from the control means and storing it, and then transmitting to said means s control the stored jump control signal, and a second memory (B 118) for receiving the black ghost control signal from said control means and storing it,   then to transmit it to said means of command.   Facsimile apparatus according to the claim   4, characterized in that the control means select-   said first image transmission method during   a predetermined number of jump control signals are reproduced and predetermined information is not present in said black ghost image signal, and in that said control means selects said second or third transmission method of when the predetermined number of jump control signals is not reproduced and / or when less than a predetermined number of said predetermined information is present in said black ghost control signal, said control means selecting the second an image transmission method, wherein a level of a blank picture element signal is less than> a high level of the synchronization signal when both the original and the recording paper are a first format, said control means selecting the third image transmission method, wherein   the level of the white picture element signal is sensitive to   equal to the high level of the synchronization signal and the phase matching is performed immediately before the transmission of the image information when both the original and the recording paper are of one second format.   The facsimile apparatus according to claim 1, characterized in that said predetermined information contained in the black ghost control signal is black information.   Fax machine according to claim 1, characterized in that the first image transmission method divides an analysis line of a sequence of picture element signals read on said original into blocks each comprising N signals. of picture elements and controls the amount of information transmitted as a function of white or black information contained in the picture element signals of each block, and that the second and third transmission methods image do not divide an analysis line of a sequence of picture element signals, read on the original, into blocks each comprising N picture element signals, and do not control the amount of pixels. information transmitted, but modulate and transmit any image element signals   white and black lines of analysis.   8 Facsimile machine according to one of the   5 and 7, characterized in that the control signal comprises a synchronization signal, a signal   control system having a predetermined number of repetitions   alternating combinations of a jump signal and the sync signal, and a black ghost image signal having a predetermined number of repetitions of the signal block including the jump signal, a signal   information and a black information signal.