JPS60136474A - Communication equipment - Google Patents

Abstract

PURPOSE:To detect assuredly only a signal sould be detected that is sent from the remote side by breaking the actuation of a detecting circuit for reception signal when a signal component similar to the reception signal is detected by a signal detecting circuit set at the transmission side. CONSTITUTION:When a PIS (procedure interruption) signal is supplied from a device of the remote side, the PIS signal appears at a port B of a hybrid circuit 1 and is supplied to a comparator 7 through a BPF6. The output of the comparator 7 is converted into a direct current by a smoothing circuit 8 and supplied to the input at one side of an AND circuit 10. While a small amount of output appears also at a port A of the circuit 1. However it is impossible for this small amount of output to actuate a comparator 4, and the output of a smoothing circuit 5 is set at ''0''. Therefore, the output of an inverter 9 is set at a prescribed level of voltage, and the circuit 10 is opened. If the transmission signal contains a large amount of the frequency component equal to the PIS signal, the output of the circuit 5 is set at a prescribed level of the circuit 5. Then the circuit 10 is closed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a communication device, and particularly to a communication device that detects a specific received signal.

[Prior art]

2. Description of the Related Art Conventionally, in order to perform bidirectional communication in communication devices such as facsimile machines, devices are well known that are provided with a so-called hybrid circuit that separates received signals and transmitted signals.

This hybrid circuit is configured to receive and detect a procedure signal transmitted from the receiving side even during image transmission. For example, a G2 (Group 2) facsimile machine that complies with the CCITT (Consultative Committee for International Telegraph and Telephone) recommendations is configured to be able to receive a PIS (Procedure Interruption) signal even during image transmission.

According to the CCITT recommendations, a single frequency of 462 Hz is used for the PIS signal. The image signal in the facsimile machine also includes this 462 Hz frequency component, but if the hybrid circuit is normal, this component will not go around to the receiving circuit side and will not be mistaken as a PTS signal.

On the other hand, as a detection circuit for the received signal, the passing center frequency is 4.
PIS with 62Hz high-Q bandpass filter
There are many configurations in which only signal components are extracted and detected.

Hybrid circuits usually have unique frequency characteristics or impedance characteristics, and if the line impedance or frequency deviates from the specified value due to the influence of frequency or other factors, the original hybrid function will deteriorate.

In this case, if the image signal to be transmitted contains a strong 462T (z component), the function of the hybrid circuit will deteriorate and the transmitted signal will go around to the detection circuit on the receiving side, causing an output to appear in the PIS signal detection circuit and malfunction. There was a drawback.

Figure 1 shows such a conventional hybrid circuit and PIS.
3 illustrates a configuration of a signal (or other procedure signal) detection circuit;

In Figure 1 (C, the one indicated by numeral 1 is a hybrid circuit and has input/output ports A, B, and C. Port A
A procedure signal and an image signal to be transmitted from the signal line 11 are input to the input terminal 1 . Further, a line such as a telephone line is connected to port C. The signal received from this line 13 is separated by the hybrid circuit 1 and output to the signal line 12 connected to port B.

That is, the hybrid circuit 1 transmits signal energy from port A to port C, but not from port A to port B, and from port C to port B. It has a transmission characteristic that it does not transmit from port C to port A.

Port B of hybrid circuit 1 has a center frequency of PIS.
A bandpass filter 6 matched to the frequency of the signal is connected. A comparator that generates a voltage at its output when the input voltage exceeds a certain set value is connected to the subsequent stage of the bandpass filter 6. Furthermore, comparator 7
A smoothing circuit 8 is connected to the latter stage. Since the output of the comparator 7 in the smoothing circuit 8 is a rectangular wave, this will be explained below using DC detection.

While an image signal or a procedure signal is being transmitted, the signal is input from port A of the hybrid circuit 1, and the signal is output to port C and sent out to the line 13. If the hybrid circuit 1 is working normally, this signal will not appear on baud)B. When a PIS signal is sent from the other device, this signal appears at port B, passes through bandpass filter 6, and is applied to the input of comparator 7.

The signal voltage level of the PIS signal at this time is
If the reference voltage plate -F is reached, a rectangular wave signal appears at the output of the comparator 7. This signal is smoothed by a smoothing circuit 8 and made into a DC detection signal.

When the hybrid circuit 1 is operating normally, the PIS signal can be normally detected as described above.

However, as mentioned above, hybrid circuit 1 often does not operate properly due to line impedance mismatch, etc., and the transmission signal input from port A often appears at a fairly strong level at port B. be. Therefore, if the image signal to be transmitted that is input to port A contains the same frequency component as the P/S signal, this component will also go around to port B, so the PI
A detection signal of the S signal will appear. In this case, there is an inconvenience in that it is not possible to determine whether the detection signal was sent by the present side or whether it was actually sent from the other party.

Furthermore, the signal sent from the other party may be a weak signal of at least -4-0 dBm according to the standards of the Telecommunications Public Corporation, etc., and the signal sent on the other hand is usually about Qd13m, which can cause the above-mentioned malfunction. This is even more of a concern.

〔the purpose〕

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and is designed to reliably detect only the signal that should be detected from the other party even when the separation of the transmitted signal and the received signal is incomplete. The purpose of this invention is to provide a communication device with

〔Example〕

The present invention will be described in detail below based on embodiments shown in the drawings. In the following, members that are the same as or correspond to those of the conventional example are given the same reference numerals, and detailed explanation thereof will be omitted.

FIG. 2 shows the configuration of the main parts of the communication equipment of the present invention.

In the present invention, the PIS signal detection circuit is almost the same as the conventional example, but the output of the smoothing circuit 8 is taken out via the AND circuit 10.

On the other hand, a detection circuit similar to the T'IS signal detection circuit is provided for debt/debt.

That is, a bandpass filter 3 , a comparator 4 , and a smoothing circuit 5 similar to the bandpass filter 6 , comparator 7 , and smoothing circuit 8 described above are connected to port A of the hybrid circuit 1 via an attenuator 2 . The attenuator 2 attenuates the transmitted signal to a certain level 1, and the center pass frequency of the bandpass filter 3 is set to be exactly the same as that of the bandpass filter 6.

The output of the smoothing circuit 5 is input to an inverter 9 that inverts the signal waveform, and the output of the inverter 9 is connected to the other input of the AND circuit 10.

In the configuration described below, when a PIS signal is input from the other party's device via the line 13, this signal appears at the port (H) of the hybrid circuit 1 and hardly appears at the port A. Therefore, the same signal passes through a band pass filter 6, and when this output has a voltage sufficient to operate a converter 7, the comparator 7 operates, and this output is converted to DC by a smoothing circuit 8, which is converted into an AND circuit. 10 inputs.

On the other hand, a small amount of output also appears in port A of hybrid circuit 1, but since this output is attenuated by attenuator 2, the output after passing through bandpass filter 3 does not operate comparator 4 and is output to smoothing circuit 5. The output becomes voltage O.

Therefore, the output of the inverter 9 becomes a predetermined voltage, which opens the AND circuit 10, and the output of the smoothing circuit 8 appears at the output of the AND circuit 10. Therefore, the output of the AND circuit 10 is transmitted to a device composed of a microcomputer or the like. ! Detection of the lllPIS signal can be performed.

On the other hand, if the transmitted signal strongly contains the same frequency component as the PIS signal, this signal will be applied to the input of the bandpass filter 3 via the 1d attenuator 2. Although the transmitted signal is attenuated by the attenuator 2, it still has a level sufficient to operate the comparator 4 even after passing through the bandpass filter 3. As a result, smoothing circuit 5
A DC detection voltage appears at the output of the inverter 9, and this voltage is inverted by the inverter 9. As a result, the AND circuit 10 is closed, so even if the hybrid circuit 1 is completely separated,
Even if the input applied to port A leaks to B and the comparator 7 malfunctions and some voltage is applied to the AND circuit 10, the AND circuit 10 is closed and the output of the AND circuit 10 is No detection signal appears.

In other words, the detection circuit on the upper side of Fig. 2 detects P in the transmitted signal.
The output of the PIS signal detection circuit shown in the lower part of FIG. 2 is cut off only when the same frequency component as the IS signal is detected. With this configuration, only the PIS signal received from the other party can be detected.

The reason for adding attenuator 2 in the above configuration is that if hybrid circuit 1 does not work at all and the input from port C appears equally on ports A and port This is to take away the operation of the detection circuit. Furthermore, this is to reduce the operating sensitivity due to the same frequency component as the PIS signal in the transmission signal.

Therefore, the attenuator 2 is not necessarily required, and instead, the response sensitivity may be set at the threshold level of the comparator 4.

In the above embodiment, the hybrid circuit 1 and the attenuator 2
The transmission signal may be input to port A by directly connecting them, or by providing an amplifier or buffer between them. As a result, when a PIS signal is received from the other party, the signal input to the attenuator 2 can be slightly reduced due to the input to the hybrid circuit 10. When configured in this way, it is also possible to omit the hybrid circuit 1.

Further, an amplifier may be provided immediately after the output of port B of the hybrid circuit 1 or immediately before the input of the bandpass filter 6. Furthermore, a detector may be provided immediately after the band filters 3 and 6 to improve detection accuracy.

Furthermore, in this embodiment, the outputs of the two hanging detectors are controlled by hardware, but the outputs of the smoothing circuits 5 and 8 are input separately to a control device such as a microcomputer, and are processed by software. You can also.

Furthermore, in the above embodiment, the PIS signal is detected by passing it through a band pass filter and detecting the voltage, but detection can also be performed by counting the number of times the signal passes through the 0 point. Of course. The detection method is not limited to 7E, and various detection methods can be used depending on the modulation method and the like.

In the above configuration, the circular S signal is exemplified as the received signal to be detected, but other signals other than the PIS signal may be used, especially if it is a procedure signal to be detected during transmission. Also,
Although the above configuration is an embodiment related to a facsimile device, the present invention can of course be implemented in other communication devices.

〔effect〕

As is clear from the above description, according to the present invention, when a signal component similar to the received signal to be detected is detected by the signal detection circuit provided in the transmission system, the operation of the received signal detection circuit is interrupted. With this configuration, it is possible to provide an excellent communication device that can reliably detect received signals.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the configuration of a conventional communication device;
The figure is a block diagram illustrating the configuration of main parts of the communication device of the present invention. 1...Hybrid circuit 2...Attenuator 3...
band pass filter

Claims (1)

[Claims] In a communication device having received signal detection means for detecting a specific received signal, a transmitted signal detection means is provided, and when the specific signal to be detected by the received signal detection means is detected by the transmitted signal detection means 7. A communication device characterized in that the received signal detection means is cut off.