JPS62172842A - Communication equipment - Google Patents

Abstract

PURPOSE:To execute satisfactorily facsimile communication by detecting a frequency of the outside of its band and its receiving level, in case when a signal has been applied to a filter of a specified band. CONSTITUTION:A BPF 2 for bringing a signal which has been inputted from a receiving signal input 3 to a band limit is provided in a MODEM 1. An output of this BPF 2 is inputted to a frequency detecting and level detecting part 4, and from this detecting part 4, a receiving frequency output 5 and a receiving level 6 are outputted to the outside as an output, for instance, as data of 8 bits. In this state, in case when a frequency of a ring-back tone and a dial tone, etc. is outside of a specified band of the BPF 2, an SW control input 9 is set to 'H' so as to changeover a switch 8 to the correcting filter 7 side. Also, in case of facsimile communication, a communication frequency is determined in advance by an advice of CCITT. Therefore, when detection of the ring-back tone and the dial tone, etc., is ended, the input 9 is set to 'L' and the facsimile communication is started.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a communication device that performs communication operations via a communication line.

[Prior art]

2. Description of the Related Art Conventionally, in this type of device, for example, a facsimile device, images of original documents and the like are communicated via a line. In this case, the facsimile signal is frequency modulated and transmitted, but only a specific frequency band is used, so the receiving side uses @f7
In order to remove the received signal, the received signal is passed through a bandpass filter for a specific band. Then, the frequency of that specific band and its reception level are detected.

However, if the received signal is applied to a bandpass filter for a specific band, it becomes impossible to detect frequencies outside the specific band and their reception levels.

In particular, when using a modem with a reception frequency detection function that has a built-in band-pass filter, the filter size is 1?
There was a drawback that it became impossible to detect frequencies outside the area and their reception levels.

[[1st aspect] The 1st aspect of the present invention is to provide a communication system that eliminates the drawbacks of the conventional example described in L and also detects signals outside the specific band of the filter even when the signal is filtered. The goal is to provide equipment.

〔Example〕

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the basic configuration of this embodiment.

In FIG. 1, 1 is a modem, and a bandpass filter 2 for band-limiting a signal input from a received signal input 3 is included in the modem. The output of this filter is input to the frequency detection and level detection section 4, and the received frequency output 5 is output as 8-bit data from this detection section.
and the reception level output 6 are output to the outside, and the frequency can be detected up to the output X20H2, that is, (θ~255)X20H2, and the reception level is the output X (-0,5 dBm), that is, (0~255) It can detect a level of 5dBm. For example, if a signal of 100OH2°-20dBm is input, output 5 will have 0O110010=
50, and output 6 outputs 00101000=40. Therefore, it is possible to use IS to know the received frequency and level using modem l, but the characteristics of bandpass filter 2 of modem l are as shown in Figure 2, and 30
Between 0 and 3400H2, the reception level does not change between the input and the filter output, but at other frequencies, the level changes and the loss is large, making it impossible to detect the frequency. Therefore, in this embodiment, a correction filter 7 having frequency characteristics as shown in FIG.
If you want to detect frequencies other than 0 to 3400H2 and detect the reception level, use SW control input 9.
By setting "H" to "H", the input of the frequency detection and level detection section has a flat frequency characteristic over all frequencies.

Next, in this embodiment, the SW control manual 9 is set to “H”.
Let's explain the case. A facsimile machine detects signals from two lines, such as a ringback tone and a dial tone. The frequency of this ringback tone or dial tone may differ depending on the region (for example, the frequency may differ depending on the country). For this reason, the frequency of a ringback tone or the like initially falls outside the band of the bandpass filter built into the modem in a certain area, and becomes undetectable by the modem.

Therefore, when the frequency of the ring bank tone, dial tone, etc. is outside the specific band of the band pass filter, the SW control manual 9 is set to "H" in order to switch the switch 8 to the correction filter 7 side as described above.

Furthermore, in facsimile communications, communication frequencies are determined by CCITT recommendations. After detection of the ring bank tone, dial tone, etc. is completed, when facsimile communication is started, the SW control 9 is set to "L" to switch the switch 8 and remove noise from the received manual signal.

In addition, the case where the SW control manual power 9 is set to the "H" level is not limited to the case described above, but also when the device is controlled using a control signal of a frequency outside the filter band as a special control signal. But that's fine.

Further, in this embodiment, a facsimile machine is taken as an example, but the present invention is not limited to facsimile machines, and can be implemented in any communication device such as a telephone or a telex shade.

〔effect〕

As explained above, even when a signal is filtered in a specific band according to the present invention, frequencies outside the band and their reception levels can be detected.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of this embodiment. FIG. 2 is a diagram showing the characteristics of the bandpass filter 2. FIG. 3 is a diagram showing the characteristics of the correction filter 7.

Claims (1)

[Claims] A first filter having a certain frequency characteristic; a second filter having a characteristic of amplifying a signal outside the frequency band of the first filter; A communication device characterized in that by applying the first filter in addition to a filter, a signal outside the frequency band of the first filter is input.