JPS62149266A - Auxiliary equipment of modem for facsimile equipment - Google Patents

Abstract

PURPOSE:To reproduce a facsimile data with fidelity by inputting an output signal of a waveform shaping circuit to an FCD input terminal of a facsimile MODE so as to attain surely the synchronization establishment of the MODEM until the end of a turn-on sequence. CONSTITUTION:The turn-on sequence signal of a G3 MODEM from an opposite side is inputted to a G3 MODEM 2 via a transformer 5, a BPF 4, a G3 AGC 3, while an output of the BPF 4 is inputted to a G2 AGC 11. Since the AGC 11 has a slow reply speed and a random noise of the next carrier period is not amplified, an L level is maintained at the square detection output of the G2 MODEM 12. However, disturbance due to noise is caused in a carrier existence period. The MODEM output is inputted to a one-short multivibrator circuit 14, and a pulse having a prescribed time width is outputted from the trailing point of time of each disturbance is outputted from a terminal Q. The output and the MODEM output are ORed by an OR circuit 15 and a signal from which the disturbance is eliminated is obtained. The signal is inputted from an output terminal 22 to an FCD input terminal 2b of the MODEM 2.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an auxiliary device for a facsimile modem, and in particular, the CCITT (International Telegraph and Telephone Consultative Committee) recommends a standard communication method as Group 3. This invention relates to an auxiliary device for a modem used in a so-called G3 facsimile machine.

[Conventional technology]

FIG. 7 is a block diagram showing the peripheral parts of the modem in a conventional 03 facsimile device, in which 1 is a facsimile control section, 2 is a facsimile control section;
is a G3 modem, 3 is a digital AGC for G3, 4 is a bandpass filter, 5 is an impedance matching transformer,
6 is a telephone line.

Data and control signals are exchanged between the G3 modem 2 and the facsimile control device 1 via a signal line 7,
Control of the G3 AGC 3 by the G3 modem 2 is performed via the signal line 8.

Terminal 2a is an output terminal for a fast carrier detection signal (FCD), and signal lines connected to this terminal 2a extend to input terminals 2b of facsimile control unit 1 and G3 modem 2, respectively. Fast carrier detection signal (FCD)
is a signal representing the presence or absence of a carrier in a signal input via the telephone line 6, and is a signal that the G3 modem 2 detects the presence or absence of a carrier and outputs as a signal representing the result.

The G3 modem 2 takes into itself the FCD that is receiving the turn-on sequence and uses it to establish its own synchronization. The reason why G3 modem 2 does not use the FCD internally but outputs it to the outside and then takes it in again from terminal 2b is due to the FCD.
This is done in consideration of the fact that there may be cases where it is desired to have a time constant when using a CD, and the user can set terminal 2a as necessary.
and 2b so that a time constant circuit can be inserted between them.

By the way, the turn-on sequence of the modem in the G3 facsimile machine conforms to CCITT, V27ter, and follows the procedure shown in FIG. As described above, the 03 modem 2 on the receiving side detects the carrier of the turn-on sequence signal sent from the transmitting side, outputs it as an FCD, and then captures it again to use it for establishing its own synchronization. In addition, the segment (
Seg,) 1 to 5 have the following contents.

Seg, 1... Unmodulated carrier Seg, 2... No energy, no carrier) Se
g, 3-180° phase inversion Seg, 4-0. 180° phase inversion Seg, 5.
..."1" scrambling [problem to be solved by the invention] However, the G3AG installed in the front stage of the G3 modem
C has a quick response to increases and decreases in the amplitude of the input signal, so when it receives a turn-on sequence signal superimposed with random noise as shown in FIG.
) as shown in Seg.

It also amplifies the random noise mixed in with 2.

Therefore, as shown in FIG. 2C, the G3 modem 2 partially detects "carrier presence" even in the Seg. 2 section, which is a section in which no carrier is present, and turns the FCD "ON". Such false detections will delay modem synchronization establishment.

In other words, synchronization should be established by the end of Seg 5, but it is now established after entering the data area, and the data from entering the data area until synchronization is established is faithful. There was a problem that it could not be reproduced.

[Means for solving problems]

The auxiliary device for a facsimile modem of the present invention has been made in view of the above problems, and includes a peak AGC for inputting a facsimile signal, a square law detection circuit for inputting an output signal of the peak AGC, and a square law detection circuit for inputting the output signal of the peak AGC. a waveform shaping circuit that inputs an output signal and removes signal cracks of a predetermined width or less in the signal, and the output signal of the waveform shaping circuit is input to the FCD input terminal of the facsimile modem. It is.

[Effect]

CCITT, V27. A fast carrier detection signal (FCD) from which the influence of random noise has been removed is obtained when a modem turn-on sequence conforming to TER is input.

〔Example〕

Hereinafter, the present invention will be described in detail along with examples.

FIG. 1 is a block diagram showing one embodiment of the present invention, and the same or corresponding parts as in FIG. 7 are given the same reference numerals. The facsimile machine shown in Fig. 1 is equipped with a G2AGC II and a G2 modem 12 in addition to a G3AGC3 and a G3 modem 2, and can function as either a G3 machine or a 02 machine by switching according to the model of the other party. .

G2AGC11 and G2 modem 12 are each controlled by facsimile control unit 1 via signal lines 18 and 19, and G2AC and C11 are controlled by facsimile control unit 1 to perform peak AGC or keyed AGC.
You can select one of the functions. Similarly, the G2 modem 12 functions as either a square law detection circuit or a synchronous detection circuit (AM-PM-VSB). In addition, such G2AC; C11
The functions of the G2 modem 12 are always required when operating as a G2 facsimile machine, and are not unique to this embodiment.

The demodulated signal output from the G2 modem 12 is sent to the facsimile control unit 1 via a signal line 20, and this signal line 20 is connected to the input terminal 21 of the waveform shaping circuit 130.
It also extends to

In the waveform shaping circuit 13, the signal line coming out from the input terminal 21 extends to the input terminal of the one-shot circuit 14, and also extends to one input terminal of the OR circuit 15 via the resistor 17. The signal line from the Q output of the one-shot circuit 14 extends to the other input terminal of the OR circuit 15, and the output signal line of the OR circuit 15 extends to the output terminal 22 of the waveform shaping circuit 13. Then, the output terminal 22 of the waveform shaping circuit 13
The signal line extending from is the FCD input terminal 2b of G3 modem 2.
and is connected to an input terminal of the facsimile control section 1. Note that 16 is a capacitor.

Next, the operation of this embodiment will be explained. When a G3 modem turn-on sequence as shown in FIG. 8 is transmitted from the other party's G3 facsimile machine, the signal is transmitted to transformer 5. The output signal of the band pass filter 4 is input to the G3 modem 2 via the band pass filter 4 and the G3 AGC 3, and at the same time, the output signal of the band pass filter 4 is also input to the G2 AGC 11. Note that the G2AGC 11 at this time is set to peak AGC, and the G2 modem 12 has a square law detection circuit selected.

Since G2AGC11 is set to peak AGC with a slower response speed than G3AGC3, random noise in the Seg, 2 section where there is no carrier is not amplified much. Therefore, as shown in Fig. 2(B), Se
During the period g, 2, the square-law detected output of the G2 modem 12 is maintained at a low level. However, on the contrary, Se
During certain carrier periods such as g, 1 and Seg, 3, cracks (bl, b) occur due to the influence of random noise.
2. b3. b4) has occurred.

The demodulated output of the G2 modem 12 is input to the one-shot circuit 14 in the waveform shaping circuit 13, and from its Q output terminal is output for a predetermined time from the falling point of each crack bl-b4. A pulse with a width T is output.

This predetermined time width T is set to a value larger than the expected maximum time width of the cracks in the G2 modem 12 output.

Then, by taking the logical sum of the demodulated output of the G2 modem 12 and the Q output of the one-shot circuit 14 in the OR circuit 15, a signal with the cracks removed in the demodulated output as shown in FIG. 2(D) is obtained. . The signal is transmitted as an FCD from the output terminal 22 of the waveform shaping circuit 13 to the FC of the G3 modem 2.
It is input to the D input terminal 2b. The FCD created in this way does not turn ON during the Seg.2 period.

FIG. 3 is a block diagram showing another embodiment of the waveform shaping circuit 13, and FIG. 4 is a timing chart. The input terminal 21 is connected to one input terminal of an AND circuit 31, and the other input terminal of the AND circuit 31 receives a high-speed clock signal as shown in FIG. 4(D) from a terminal 32. The output terminal of the AND circuit 31 is connected to the B input terminal of the one-shot circuit 14, and the Q output terminal of the one-shot circuit 14 is connected to the output terminal 22 of the waveform shaping circuit 13.

In this configuration, when a demodulated signal (FIG. 4 (B) and (C)) similar to that of the first embodiment is inputted from the G2 modem 12 to the input terminal 21, the clock signal (FIG. 4) is input to the AND circuit 31. (D)) is logically ANDed with (D)) in Figure 4 (
Obtain the signal shown in E). When the one-shot circuit 14 is sequentially triggered by the output signal of the AND circuit 31, it is possible to obtain as the output of the one-shot circuit 14 a waveform in which the cracks bl and b2 occurring in the period of Seg, 1 are removed, for example. It is possible (Figure 4 (F)
)). Note that, as in the case of the first embodiment, the output pulse width T of this one-shot circuit 14 is set to a value larger than the expected maximum time width of the cracks in the output of the G2 modem 12 formed by random noise. I'll keep it.

FIG. 5 is a block diagram showing still another embodiment of the waveform shaping circuit 13, and FIG. 6 is a timing chart in this embodiment. In this embodiment, an interval timer 51 and a flip-flop circuit 52 are used in place of the one-shot circuit 14.

The input terminal 21 is connected to the input terminal of the knot circuit 53,
The output terminal of the NOT circuit 53 is connected to the gate terminal of the interval timer 51. Interval timer 51
Its CK input terminal is connected to the input terminal 32 of the high-speed clock signal, and its output terminal is connected to the cp input terminal of the FF circuit 52. Further, the R input terminal of the FF circuit 52 is connected to the input terminal 21 , and the Wataru output terminal is connected to the output terminal 22 of the waveform shaping circuit 13 .

In this configuration, when the demodulated output of the G2 modem 12 (FIG. 6 (B), (C)) is input to the input terminal 21, the signal is input as it is to the R terminal of the FF circuit 52, and at the same time, the signal is input to the NOT circuit. 53 ((D) in the same figure),
The signal is input to the gate of the interval timer 51. A high-speed clock signal as shown in FIG. 6(E) is input to the CK input terminal of the interval timer 51, and when the gate signal is at a high level continuously for a predetermined period of time, its output signal falls instantaneously. Since this predetermined time T is set to a value larger than the expected maximum time width of the cracks in the G2 modem 12 output caused by random noise,
It does not fall due to a crack in the G2 modem 12 output, and the 6th
A waveform like that shown in Figure (F) is obtained. Then, the FF circuit 52 is operated using this signal, and a signal as shown in FIG. 6(G), that is, an FCD from which the influence of random noise has been removed, is obtained as the output of the waveform shaping circuit 13.

In this embodiment, in order to obtain the signal before the waveform shaping circuit 13, the G2AGC 11 and G2
2 modems 12 are used. Therefore, the present invention can be implemented at extremely low cost, but it goes without saying that the present invention can also be implemented in a G3-specific facsimile machine if a dedicated peak AGC and square law detection circuit are provided.

〔Effect of the invention〕

As explained above, according to the auxiliary device of the present invention, the CCI
TT, V 27. If the turn-on sequence of the modem is manually performed in accordance with TER, it is possible to obtain a high-speed carrier detection signal (FCD) from which the effects of random noise have been removed, ensuring that synchronization of the modem is achieved by the end of the turn-on sequence. , facsimile data is always reproduced faithfully from the beginning.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a timing chart thereof, FIG. 3 is a block diagram showing another embodiment of the waveform shaping circuit 13, and FIG. 4 is a timing chart thereof. FIG. 5 is a block diagram showing still another embodiment of the waveform shaping circuit 13, and FIG. 6 is its timing chart.
Figure 7 is a block diagram showing the conventional configuration, Figure 8 is a CCI
TT. V27. FIG. 9 is a timing chart for the conventional example shown in FIG. 7. 2...G3 modem, 2b...FCD input terminal, 11
...G2AGC212...G2 modem, 13...
Waveform shaping circuit. Patent applicant: Tamura Electric Manufacturing Co., Ltd. Representative: President Yamakawa (and 2 others) Figure 2 1+5eg, l +Seg, 22-1-5e, 3-+-
CD) +5opF Figure 5

Claims (1)

[Claims] In a facsimile modem used in a G3 facsimile machine and equipped with an FCD input terminal, a peak AGC inputs a facsimile signal from a line, a square law detection circuit inputs an output signal of the peak AGC,
a waveform shaping circuit that inputs the output signal of the square law detection circuit and removes signal cracks of a predetermined width or less in the signal,
An auxiliary device for a facsimile modem, wherein an output terminal of the waveform shaping circuit is connected to an FCD input terminal of the facsimile modem.