GB2239370A

GB2239370A - Facsimile device transfer control

Info

Publication number: GB2239370A
Application number: GB9010881A
Authority: GB
Inventors: Sumio Sekigawa
Original assignee: Funai Electric Co Ltd
Current assignee: Funai Electric Co Ltd
Priority date: 1989-12-21
Filing date: 1990-05-15
Publication date: 1991-06-26
Anticipated expiration: 2010-05-15
Also published as: JPH03192873A; HK193696A; GB9010881D0; JP2568445B2; DE4019953C2; DE4019953A1; GB2239370B

Abstract

A facsimile device stores data representative of the level of an incoming training signal, and determines the starting point for receiving a picture signal when the incoming level after transmission of a CFR (Confirmation to Receive) signal is larger than a threshold level which is lower than the abovementioned stored incoming level by predetermined amount. The picture signal can be received with stability even when the circuit echo occurs. <IMAGE>

Description

9 11 FACSIMILE DEVICE The present invention relates to an apparatus for

detecting an incoming image signal in.a facsimile device.

In conventional facsimile devices, the image or picture signal is transferred after executing a predetermined procedure of transfer control between a called subscriber and a calling subscriber. In the procedure of transfer control, there is a device in which a CFR (confirmation to Receive) signal is sent to the calling subscriber by the called subscriber after reception of a training signal, then, an image signal is received in response to the CFR signal.

When a circuit echo occurs in a loop between the transferring and receiving in an international telecommunication via satellite, it becomes difficult to detect the period when there is no signal and the starting point for receiving an image signal sent in response to a UR signal. As a result it is sometimes difficult to receive image data in a group 3 (G3) device even when the training signal can be received in the transfer control procedure.

An aim of the present invention is to provide a facsimile device in which the image data can be received with stability even when the circuit echo occurs as mentioned above.

According to the present invention, there is provided a facsimile device having a means for executing a transfer 4 1 control procedure comprising transmitting a CFR.(Confirmation to Receive) signal to a calling subscriber after reception of a training signal by the called subscriber, and receiving an image signal sent in response to the CFR signal, the device comprising; means for storing data representative of the level of the incoming training signal, and means for detecting whether or not the level of input after transmission of the CFR signal is greater than a threshold level, the threshold level being lower than the stored level by a predetermined amount; and means for determining the starting point for receiving an image signal when the level of the input is higher than said threshold level.

Generally, the amplitude of the incoming signal such as the training signal and the like in the procedure of transfer control is nearly equal with that of the image signal. By contrast, the amplitude of an echo signal is rather smaller, therefore, in the structure of the present invention. by taking the starting point for receiving the picture signal as the time of receipt of a signal which is larger than the threshold level. which itself is lower than the level of the incoming signal such as the training signal and the like, by a predetermined amount, the picture signal can be received with stability without being influenced by noise from the circuit echo.

1 The present invention will be further explained hereinafter with reference to. the following description of an exemplary embodiment and the accompanying drawings, in which:

Fig. 1 Is a block diagram of a facsimile device of an embodiment of the present Invention; Fig. 2 Is a schematic view showing a procedure of transfer control of the device; Figs. 3 (a) (b) are time charts of an incoming signal at ordinary time and at time when the circuit echo occurs respectively; and Fig. 4 is a flow chart of the procedure of transfer control.

Fig. 1 is a block diagram showing the structure of one embodiment of a facsimile device according to the present Invention. The facsimile device comprises a facsimile control section 1 (Central Processing Unit) for executing transfer control Including predetermined procedure, a picture signal processing section 2 for reading out a manuscript to transfer and for processing the signal thereof, and a picture signal recording section 3 for recording picture data obtained from received signal. Further, the device Is connected to a circuit 6 through a modem section 4 and an Inputoutput circuit 5, and the end of k the circuit 6 Is connected to a device in opposite side (a calling or a called subscriber).

Fig. 2 shows a schematic view of the procedure of transfer control of the facsimile device between the calling subscriber and the called subscriber. In Fig. 2, the called subscriber receives a DCS (Digital Command Signal) and a training signal outputted from the calling subscriber, and when functions such as linear density and encoding system or an operating mode are fit for the called subscriber, the called subscriber outputs the CFR (confirmation to Receive) signal to the calling subscriber. When the calling subscriber receives the CFR signal, it outputs a picture signal in response to the CFR signal.

Figs. 3 (a) (b) show time charts of an incoming signal at ordinary time and at time when the circuit- echo occurs respectively, and Fig. 4 shows a flow chart of an operating procedure according to the present operation. A oblique line part In Fig. 3 (b) shows a noise signal occurred by the circuit echo. When the circuit echo occurs, after transferring the OFR signal, It becomes difficult to detect the starting point for receiving a picture (document) signal which Is a response signal thereof. Therefore, In this embodiment, data of an Incoming level LR during receiving a training signal which Is confirmable to being Identified, Is stored In a memory In the facsimile control section 1 In the called subscriber, then, after transferring the CFR signal, the Incoming level (LIR) that is a value lower than t 1 i the level LR stored in the memory by predetermined value a, is designated as a threshold level (LR-a). When the signal larger than the threshold level is received, it is judged to be the starting p oint for receiving the picture document) signal.

The predetermined value a may be determined properly in consideration of the change of the signal. For example, the lowest Incoming signal level at ordinary time is about -47 to -43 dBm, and the Incoming signal level is actually -30 dBm on average. Since it is appreciated that the echo signal level is lower than the above Incoming signal level by 10 dB or more, the Incoming level LIR after transferring CFR signal becomes -36 dBm when the predetermined value a is -6 dB.

Now, operations according to the present invention will be described with reference to a flow chart shown in Fig. 4. As a result of a training, when there is no problem (YES at #1), the incoming level LR during training term is stored in the memory (#2), then the CFR signal is transferred (#3). Whether or not the incoming level LiR afterward Is larger than LR-a is detected (#4), and when it Is judged to YES at #4, receiving the manuscript signal Is started (#5). By executing the abovementioned procedure of transfer control, even when the circuit echo occurs, the normal incoming signal can be distinguished from the echo signal so that the normal incoming signal can be received stably.

As being apparent from the abovementioned description,

1 according to the present invention, the level of the incoming signal such as the training signal which Is surely distinguishable from noise signal Is picked up as reference level, and the Incoming signal afterward Is compared with the threshold value which Is lower than the above reference level by predetermined value. When the Incoming signal Is larger than the threshold level, It Is judged to be a normal signal, and therefore, the normal Incoming signal can be received with stability even when the circuit echo occurs.

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Claims

1. A facsimile device having a means for executing a transfer control procedure comprising transmitting a UR (Confirmation to Receive) signal to a 'calling subscriber after reception of a training signal by the called subscriber, and receiving an image signal sent in response to the UR signal, the device comprising; means for storing data representative of the level of the incoming training signal, and means for detecting whether or not the level of input after transmission of the CFR signal is greater than a threshold level, the threshold level being lower than the stored level by a predetermined amount; and means for determining the starting point for receiving an image signal when the level of the input is higher than said threshold level.

2. An apparatus constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Published 1991 at The patent Ofilce. State House. 66171 High Holbom. London wcj R 41P. Further copies rmy be obtained frorn Sake Branch, Unit 6. Nine Mile point, Cwmfchnfach, Croas Keys. Newport. NPI 71AZ. Printed by Multiplex techniques lid. St Mary Cray. Kent.