JPS6037876A - Control signal detecting system in facsimile - Google Patents

Abstract

PURPOSE:To ensure the detection of control singals by making an ON period of a switch that introduces the signal to a filter that passes control signals from a receiver minimum period in which the control signal can be detected including carrier sending period. CONSTITUTION:A facsimile transmitter 1 transmits a transmitting signal S1 sent out from a transmitting unit 4 to a receiver 2 through a circuit 3. The receiver 2 transmits a control signal S2 through the circuit 3. The generating period of the signal S2 includes carrier sending period included in the signal S1. The signal S1 and signal S2 are added and sent to a filter 6 through a switch 5. The switch 5 is controlled by a CPU and its ON period is minimum period in which the filter 6 can detect the signal S2 including the carrier sending period. By making ON period of the switch 5 necessary minimum, the erroneous detection of the signal S1 by the filter 6 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for a transmitter to reliably detect various control signals sent from a receiver to a transmitter during analog mode facsimile communication.

The outline of the facsimile transmission signal (Sl) in analog mode is as shown in Figure 1 (A), and each line (L) of the signal (Sl) is an image in which image information (a) is superimposed on a carrier (C). An image signal transmission period (T1) with a signal (l) and a carrier transmission period (T2) with only a carrier (C)
). There are two types of facsimile communication: full-duplex and half-duplex. In the former, the line for sending the above-mentioned transmission signal is separate from the line for the control signal (S2) issued by the receiver during communication, and in the latter, The above transmission signal (S
1) and the control signal (S2) are passed through in common. The second control signal (S2) has a specific frequency and is used to issue a communication request from the receiver, such as a command to stop communication, to the transmitter, and in the case of analog mode communication, the control signal The signal (S2) is transmitted during the image signal transmission period (TI) and the carrier transmission period (TI) as shown in FIG.
t2). The image signal (I) includes various frequencies depending on the image information (a), and also includes the same frequency as the control signal (S2), so it is half-duplex, that is, on the same line. The above control signal (S2
), the receiver sends a control signal (S2
) is not emitted, the above image signal (
b) The transmitter may detect the same frequency component as the control signal in the transmitter and automatically stop communication.

The present invention has been made in view of the above-mentioned circumstances, and in facsimile communication in half-duplex analog mode,
It is an object of the present invention to provide a detection method that can reliably detect only control signals from a receiver.

Embodiments of the present invention will be described below based on the drawings.

FIG. 2 shows an apparatus for implementing the present invention, in which a facsimile transmitter (1) and a facsimile receiver (2) are communicating in an analog mode via a single line (3). (4) is a transmitting device equipped with a reading device for a transmission original, an encoding device, a modulator, etc., and from the transmitting device (4), a transmission signal (Sl) as shown in FIG. is transmitted, and while the transmission signal (Sl) is being transmitted, the receiver (2) transmits the control signal (S2) shown in FIG. Transmitter (1)
The control signal (S2) that has reached is added to the transmission signal (Sl) emitted from the transmitter (1) and sent to the switch (5).
As shown in the figure, when the switch (5) is in the ON position, the signal is input into the next stage filter (6). The switch (5) is switched and controlled by a control device such as a CPU (not shown), and the filter (6) is a narrowband bandpass filter that passes only the control signal (S2) and sends it to the control device.

Opening/closing of the switch (5) and detection of the control signal (S2) by the filter (6) are performed as follows. Figure 3 (A) shows the signal sent to the switch (5), that is, the transmission signal (Sl) with a control signal (S2) indicated by diagonal lines added, and Figure 3 (B) shows the signal sent to the switch (5). The opening/closing operation is shown in FIG. Carrier sending period for one line (L) (
T2) is only a few percent, but the length of each line (I,) is constant, and therefore the timing of the carrier sending period (T2) is fixed, so the control device controls the switch (5). is set to a period and range that can reliably include the carrier sending period (T2), and only this period (T3) is set as shown in Fig. 3 (
Turn it on as shown in b). The above switch ON period (T
3) is much longer than the carrier sending period (T2), a part of the image signal (1)) is inputted to the filter (6) and is the same as the control signal (S2) included in the image signal (1)). There is a possibility that the filter (6) may cause a detection error due to the frequency component. Furthermore, if the switch ON period (T3) is too short, the control signal cannot be detected by the filter (6). As mentioned above, the carrier sending period (T2) is extremely short, so even if the switch ON period (T3) is the same width as the carrier sending period (T2), it is often difficult to detect the control signal, so this In this method, the switch ON period (T3) is set to the minimum period that includes the carrier sending period (T2) and allows the control signal frequency to be detected by the filter (6). The above-mentioned minimum period means that even when the control signal (S2) exists and there is no component of the same frequency as the control signal in the image signal (b), the filter (6) does not respond to the control signal (S2).
This refers to a period in which the control signal (S2) can be reliably detected and in which erroneous operation will not occur even if the control signal (S2) is not present and there are many components of the same frequency in the image signal (b). In the case of Gl mode in which the control signal (S2) is 462 Hz, the switch ON period (T3) is preferably about 22 m5ec, which is about three times the carrier sending period (T2). switch O
By setting the N period (T3) as described above, the filter (6) receives the control signal (S2) as shown in FIG.
The facsimile transmitter (1) is detected reliably.
starts a predetermined operation.

As explained above, according to the present invention, the transmitter can reliably detect various control signals from the receiver, and various troubles in communication can be solved.

[Brief explanation of drawings]

Figures 1 (a) and (b) are diagrams for explaining transmission signals and control signals, respectively, Figure 2 is a diagram showing a circuit for implementing the present invention, and Figure 3 is a diagram for explaining the present invention. In the figure, (a) shows the signal flowing into the switch, and (b) shows the signal flowing into the switch.
is a diagram showing the operation of the switch, and (c) is a diagram showing the operation of the filter. (1)・Facsimile transmitter (2)Facsimile receiver (5)Switch (6)・Filter (a)・
- Image information (b) - Image signal (C) - Carrier (L)...Line (31) -
Transmission signal (S2) Control signal (TI) Image signal transmission period (T2)/Carrier transmission period (T3) Switch ON period

Claims (1)

[Claims] Control sent from the receiver to the transmitter in analog mode half-duplex facsimile communication consisting of an image signal transmission period in which each line of the transmission signal from the transmitter has image information and a carrier transmission period in which only the carrier is present. A method for detecting a signal, comprising: a filter that allows only the control signal to pass; and a switch that controls introduction of the transmission signal and the control signal into the filter, the method including the carrier sending period and controlled by the filter. A control signal detection method for a facsimile machine, characterized in that the switch is turned on only during a minimum period during which a signal can be detected.