JP2817417B2 - Noise level measurement method for telephone lines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a noise level of a telephone line.

[0002]

2. Description of the Related Art Recently, a facsimile apparatus for transmitting image information via a telephone line has been developed and used. However, in such a facsimile, after a telephone line is connected, Until transmission of image data is started, data necessary for facsimile transmission is mutually transmitted.

FIG. 3 shows a schematic sequence of such data transmission. When a called party receives a call by a call from the calling party and a telephone line is connected, the calling party sends a call to the called party. A CNG signal (non-voice terminal identification signal) is transmitted, and the called side receives the CNG signal a predetermined time after the line is connected.
CED signal (called terminal identification signal) which is a response signal of the signal
To recognize that both are facsimile. Then, a DIS signal (digital identification signal) is transmitted from the called side to the calling side, and a DCS signal (digital command signal) is transmitted from the calling side to the called side to perform mutual function setting. Then, the process proceeds to a training sequence for determining a communication speed for transmitting image data. When the training sequence ends, the transmission sequence of the image data starts at the determined communication speed. As described above, after the telephone line is connected, data transmission is performed without interruption between the calling side and the called side by handshake.

[0004] By the way, noise generated from a telephone exchange or the like is superimposed on a telephone line or noise from a noise source near the telephone line is often mixed into the telephone line. If received, the transmitted and printed image information will have speckles, etc., depending on the noise, and if it is interrupted during the handshake of data required for facsimile transmission, it will not be possible to perform a normal handshake. When a communication error occurs, if the quality of the transmitted image is poor or the communication error occurs frequently, a serviceman measures the noise of the telephone line with a dedicated level measuring instrument and the noise level reaches the specified value. If it does, measures have been taken to ask the central office for improvement.

However, in order to measure the noise of the telephone line, the telephone line is connected between the calling side and the called side, and the signal level of the telephone line when no signal is transmitted is measured. Must be measured, but as mentioned above,
After the telephone line is connected, it is practically impossible to accurately measure the noise level of the telephone line because signal transmission is performed between the calling side and the called side without interruption.

[0006]

SUMMARY OF THE INVENTION The present invention, proposed in view of the above circumstances, is intended to transmit a signal on a telephone line in a state where a facsimile between a calling side and a called side is connected via the telephone line. An object of the present invention is to provide a telephone line noise level measuring method in which a standby state is caused to generate a no-signal transmission period, whereby the telephone line noise level can be easily measured.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention proposes a method of measuring the noise level of a telephone line using a facsimile. When receiving a control signal requiring a response signal transmitted from the facsimile of the station, ignore the received control signal or generate a signal-free transmission period by transmitting a signal different from the response signal, and this During the period, the noise level of the telephone line is measured. In such a facsimile apparatus for carrying out the method of the present invention, it is desirable that the facsimile apparatus has a configuration in which a measurement mode for measuring a noise level and a normal mode for performing normal facsimile transmission can be selected.
It is also possible to incorporate a noise level measurement circuit and display the measured noise level of the telephone line on a display or the like.

[0008]

According to the present invention, a call is originated at the own station or the partner station, and after the telephone line is connected to the facsimile of the partner station,
When a control signal requiring a response signal is transmitted from the facsimile of the partner station, the transmitted control signal is ignored or a signal different from the response signal is transmitted to the partner station. Then, in the facsimile of the partner station, there is a non-signal transmission period in which no signal transmission is performed in order to wait until a response signal to the transmitted control signal is returned, so that the signal level of the telephone line is easily adjusted during this period. Measurement, which makes it easy to know the noise level.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a flow chart showing the method of the present invention. Referring to FIG. 1, when a call is made by a facsimile of the own station or a partner station previously contacted, the facsimile of the own station and the facsimile of the partner station are transmitted. A telephone line is connected between them. When a control signal requiring a response signal (for example, a CNG signal indicating a non-voice terminal) is transmitted from the facsimile of the partner station, a response signal (a called terminal identification signal (CED signal which is a response signal to the CNG signal)) is transmitted. Signal)), and ignores the resulting received CNG signal. Then, the facsimile of the partner station waits until a response signal to the transmitted control signal is returned, so that no signal is transmitted during the standby period, and the signal level (noise level) of the telephone line is set during this period. level)
Is measured. (The above, (A) step 100-1 of FIG.
03).

FIG. 1B is a flowchart showing another example of the method of the present invention. In the method shown in FIG. 1A, a control signal requiring a response signal is transmitted. When it comes, it is different in that it transmits (replies) an unrelated signal different from the response signal, and the other parts are the same. (As above, FIG. 1 (B)
See steps 200-203).

In the present invention, as described above, the control signal transmitted from the partner station side is, as described above, a CNG signal transmitted immediately after the telephone line is connected, or a control signal transmitted in a training sequence. Various signals that require a response signal such as a TCF signal (training check signal) can be applied. In the case of a CNG signal, the CED signal, which is a response signal, is not returned so that a non-signal transmission period is set. In the case of a TCF signal, a non-signal transmission period can be generated by not returning a CFR signal (reception preparation confirmation signal) or an FTT signal (training failure signal) as a response signal. As described above, according to the method of the present invention, in a state where the telephone line is connected between the facsimile of the own station and the facsimile of the partner station, a no-signal transmission period can be generated. The noise level of the telephone line can be measured.

FIG. 2 is a block diagram showing an example of the internal configuration of the facsimile apparatus 1 for carrying out the method of the present invention. In FIG. 2, reference numeral 10 denotes a signal processing unit for performing signal processing of each unit; Is a key operation unit having various operation keys (not shown), 12 is a mode switching unit for switching and setting between a measurement mode and a normal mode described later, 13 is a line control unit for switching connection of the telephone line L, Reference numeral 14 denotes a signal level detection circuit for detecting the signal level of the telephone line L, and reference numeral 15 denotes a display unit for displaying the signal level detected by the signal level detection circuit 14 and various displays. 16 is a telephone line L
Modem for transmitting and receiving image data and the like via
Is a system memory having a ROM 17a and a RAM 17b, 18 is a print output unit that prints out image data received and demodulated by the modem 16 on recording paper, and 19 is an image reading unit that reads image information of a transmission original and converts it into image data. Department.

The mode switching section 12 switches between the measurement mode and the normal mode. When the mode is switched to the normal mode, the signal processing section 10 stores the data in the ROM 17a of the system memory 17. A normal facsimile transmission process is performed by activating the facsimile transmission processing program. When the mode is switched to the measurement mode, the signal processing unit 10 activates the measurement processing program stored in the ROM 17a, and the telephone line L is connected. After that, even if a CNG signal is transmitted via the telephone line L, the CED signal, which is a response signal, is ignored without being returned. The signal level detection circuit 14 always detects the voltage level of the telephone line L (in this embodiment, detects the effective value), and causes the display unit 15 to display the detected voltage level data.

The operation of the facsimile 1 in the measurement mode for implementing the method of the present invention having such a configuration will be described below. It is assumed that the facsimile 1 is the called side. When a mode switch (not shown) of the key operation unit 11 is switched to the measurement mode, the mode is switched to the measurement mode by the mode switching unit 12.
The measurement processing program stored in M17a is started. When a call signal is transmitted via the telephone line L, the signal processing unit 10 determines whether the call signal has been received, and transmits a control signal to the line control unit 13 to automatically receive a call. When a CNG signal is transmitted via the telephone line L,
The signal processing unit 10 identifies the CNG signal, but does not transmit the CED signal as a response signal, and thus ignores the CNG signal. On the calling side, the telephone line L enters a no-signal transmission state in order to wait for the CED signal as a response signal to be returned. By reading, the noise level generated in the telephone line L is measured. When a predetermined time elapses without returning a response signal, the calling side performs a communication error process and disconnects the line.
In the above, instead of the operation of ignoring the transmitted CNG signal, a signal different from the CED signal as a response signal may be transmitted (replyed).

As described above, according to the facsimile 1 for carrying out the method of the present invention, it is possible to automatically generate a no-signal transmission period simply by switching to the measurement mode and starting facsimile reception. If the signal level of the telephone line L during this period is read by the display unit, the noise level can be easily obtained.

In the facsimile 1 described above, a measurement mode is provided to automatically generate a no-signal transmission period. However, the present invention is not limited to such a configuration, and a call can be made using a normal facsimile. When the user receives a call and immediately operates the start key, the CNG signal transmitted from the calling side and the CNG signal transmitted from the local station to the calling side are competed on the telephone line L. It is also possible to generate a signal-free transmission period, during which the signal level of the telephone line can be measured. Further, in the facsimile 1 described above, the signal level detection circuit 14 detects the effective value of the signal level of the telephone line L.
If necessary, the peak value and the time average value can be detected. If the modem 16 has a function of detecting the signal level of the telephone line L without providing the signal level detection circuit 14 in particular. May display the signal level detected by the modem 16. Further, in the facsimile 1 described above, the mode is switched to the measurement mode by operating the mode switching switch provided on the key operation unit 11. However, the mode switching switch is provided inside the facsimile 1 and only the service person can operate. Is also good.

[0017]

As will be understood from the above description, according to the method for measuring the noise level of a telephone line according to the present invention, a control signal requiring a response signal transmitted from a partner station after connection of the telephone line is ignored. Alternatively, by simply transmitting a signal different from the response signal, a no-signal transmission period can be generated, and during this period, the noise level of the telephone line can be easily measured.

[Brief description of the drawings]

FIGS. 1A and 1B are flowcharts illustrating the method of the present invention.

FIG. 2 is a diagram showing an example of the internal configuration of a facsimile for carrying out the method of the present invention.

FIG. 3 is an explanatory diagram showing a sequence of signals transmitted between a calling side and a called side in a normal facsimile.

[Description of Signs] 1 Facsimile L Telephone line CNG signal Control signal CED signal Response signal

Claims (1)

(57) [Claims] 1. A method for measuring a noise level of a telephone line using a facsimile, comprising the steps of: receiving a control signal requiring a response signal transmitted from a facsimile of a partner station after the telephone line is connected; A noise in the telephone line that causes a signalless transmission period by ignoring the received control signal or transmitting a signal different from the response signal, during which the noise level of the telephone line is measured. Level measurement method.