JPH0517736B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is used, for example, in a line quality measuring device that measures the on-time of various tone signals, etc., which is a test item for the line quality of a telephone line network. The present invention relates to a signal receiving device, and particularly to a signal receiving device provided with means for preventing the influence of impulsive noise.

(Prior Art) Generally, terminal equipment for various purposes connected to the subscriber end of a telephone line network establishes an interface with an exchange while detecting various tone signals such as dial tone, ringback tone, and busy tone. I'm making a call. These tone signals are a single sine wave signal with a specified signal level that is controlled on and off at certain time intervals as shown in Figure 5. For example, a dial tone is a 400Hz continuous wave signal. Send out (Figure 5a), the ring back tone is turned on and off with an on time of 1 sec and an off time of 2 seconds (Figure 5 b), and the busy tone is turned on and off with an on time of 500 msec and an off time of 500 msec. (Fig. 5c). Therefore, it is necessary to identify the nature of such signals in order to establish an interface with the exchange.

On the other hand, as a terminal device that interfaces with an exchange, especially a line quality measurement device, it is important to accurately measure the arrival time of dial tone after on-hook and the arrival time of ring back tone after dialing. It is considered very important as a test item to understand the condition.

Incidentally, in order to accurately measure the on-time of the various tone signals as described above, a signal receiving apparatus having a configuration as shown in FIG. 6 is used. That is, this device compares a filter 1 that extracts frequency components such as tone signals with a predetermined reference level and the output of this filter 1, and determines the on-time when the output level of the filter 1 exceeds the reference level. and a threshold detection circuit 2 which outputs a "1" level signal indicating the off time, and outputs a "0" level signal indicating the off time when the signal is below the reference level, and from the output of the threshold detection circuit 2. Identifying tone signals.

(Problems to be Solved by the Invention) However, in general, in this type of telephone line network, high-level impulsive noise as shown in Figure 7a is generated during the line connection operation of the exchange, and this noise The signal is received by the signal receiving device along with the dial tone and ringback tone signals. At this time, this signal receiving device is configured to faithfully receive only the tone signal without receiving noise, but if impulsive noise is input, it will have a level as shown in Figure 7b. It is converted into an on/off signal and is received as an original signal.
As a result, there is a problem that automatic response terminal equipment that automatically receives tone signals from the exchange side and connects lines, etc., often malfunctions due to the above-mentioned impulsive noise. Such problems can occur even when a line quality measurement device is connected to the telephone line network, and the line quality measurement device is used to connect the line with the other party and measure the line quality during that time. A problem arises.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a signal receiving device that can receive original signal components without being affected by impulsive noise.

(Means for Solving the Problems) A signal receiving device according to the present invention cuts low-frequency components of impulsive noise from an input signal that includes a sinusoidal regular signal having a specified signal level and impulsive noise. a low-pass filter, a period when the output of this low-pass filter is a positive signal component, a charging circuit that charges the low-pass filter output to a capacitor connected to the other end, and a period when the output of the low-pass filter is a negative signal component. , a discharging circuit that discharges the charging energy of the capacitor and a switching circuit are provided between one end of the capacitor and the ground, and a high-level impulsive noise that exceeds a predetermined level set above the specified signal level of the input signal is The charging circuit is equipped with a suppressing means that closes the switching circuit in response and forcibly discharges the charging energy of the capacitor, so that only the original normal signal component is extracted from the charging circuit.

(Function) Therefore, by using the above means,
A low-pass filter cuts out the low-frequency components of impulsive noise contained in the input signal, and charges the output of the low-pass filter when it is a positive signal component.
Discharges when the signal component is negative. At this time, if the input signal includes high-level impulsive noise, the suppressing means receives the impulsive noise and suppresses it by forcibly discharging the energy charged in the charging circuit using another discharge system. do. As a result, the energy of the charging circuit charged by the impulsive noise does not reach the reference level for obtaining the on-time signal, and the impulsive noise does not cause malfunction.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the application locations of the signal receiving device according to the present application. In general, this type of telephone network system has a dial pulse sending contact 13 and a DC blocking capacitor 14 interposed between an exchange subscriber circuit 11 and a hybrid coil 12, as shown in FIG. A signal transmitting device 15 for transmitting a dial tone or other necessary signals, such as a signal for measuring line quality, is connected to the intermediate terminal of the other winding of the coil 12, and further, a signal transmitting device 15 for transmitting a dial tone or other necessary signal, such as a signal for measuring line quality, is connected to the outer terminal of the other winding. A related signal receiving device 16 is connected. 17
18 is a control unit that detects a transmission command or an incoming call state and provides necessary control signals to appropriate components;
When making a call, the dial pulse sending contact 13 receives a control signal from the control unit 17 and gives a signal for sending a dial pulse to the dial pulse sending contact 13 to send out the dial pulse, and when receiving a call, the dial pulse sending contact 13 receives a control signal from the control unit 17 and sends out a dial pulse based on the incoming call detection signal. This is a dial pulse sending circuit that connects 13.

However, in the above system,
For example, when making a call, after confirming the dial tone from the off-hook exchange (not shown) via the signal receiving device 16, a control signal is output from the control unit 17 to control the dial pulse sending contact 13 on and off. and sends out a dial signal. Thereafter, the signal receiving device 16 is used to detect the ring back tone and confirm the connection response from the other party. In measuring the line quality of a telephone line network, after the line is connected in the same manner, a line measurement signal is sent out and the signal receiving device 16 measures the line quality.

Incidentally, the impulsive noise generated in the telephone line network system and other data communication lines as described above has the following properties. In other words, one of them is that it appears in a short time and the time average energy is very small, the other one is that it contains low frequency components, and furthermore, the instantaneous maximum voltage is 0 dBm or more and the voltage level is 20 For example, the voltage is about ~40V.

Next, FIG. 2 is a block diagram showing a specific example of a signal receiving device according to the present invention realized based on the above characteristics. In the figure, reference numeral 21 denotes an input terminal that receives an input signal input from the hybrid coil 12 side, which includes, for example, a sinusoidal regular signal having a specified signal level consisting of various tone signals and impulsive noise. A low-pass filter 23 is connected through a filter 22 having a band for extracting the required signal. The reason for providing this low-pass filter 23 is that the filter 22
This is because impulsive noise containing low to high frequency components cannot be completely removed using the method. Therefore, the low-pass filter 23 particularly cuts out the low-frequency components of impulsive noise. This low pass filter 2
A charging circuit 24 for charging the positive signal component output from the filter 23 and a discharging circuit 25 for discharging the energy charged in the charging circuit 24 are connected to the output side of the filter 3.

Specifically, the charging circuit 24 has a diode D ₁ interposed between the output side of the low-pass filter 23 and the ground to take out a positive signal component, and a diode D ₂ and a resistor from the output side of the low-pass filter 23 . connected serially in the order R ₁ and capacitor C,
The other end of the capacitor C is grounded. On the other hand, in the discharge circuit 25, a serial circuit of a diode _D3 and a resistor _R2 is connected in parallel across the diode _D2 and the resistor _R1 , and a resistor _R3 is connected between the output side of the low-pass filter 23 and ground. This is an intervening configuration.

26 is a capacitor C that operates when the input signal is at a predetermined level and constitutes a part of the charging circuit 25.
This is a suppression means that forcibly discharges the energy charged in the battery. This suppressing means 26 has an input terminal 2
A relay 27a that operates when the level of the signal input to the input terminal 1 is at a predetermined level set to be higher than a specified signal level of a regular signal such as a tone signal, and a contact that closes and performs a grounding operation by the operation of this relay 27a. 27b etc., a contact point 27b of this impression switch 27, and the capacitor C.
A diode D4 is connected between the capacitor C and a directional diode _D4 that discharges the charging energy of the capacitor C.

28 is a threshold detection circuit, and this circuit 2
8 compares the output of the charging circuit 24 with a predetermined reference voltage, and when the charging voltage exceeds the reference voltage, outputs a "1" level signal, that is, an on-time signal;
It has a function of outputting a "0" level signal, that is, an off-time signal, when the voltage is below the reference voltage.

Next, the operation of the apparatus configured as above will be explained. For example, suppose that a signal containing impulsive noise is input from the hybrid coil 12 through the input terminal 21. This impulsive noise passes through a filter 22, and a low-frequency filter 23 cuts off the low-frequency noise, and a diode D1 of a charging circuit ₂₄ charges the capacitor C with only the positive signal component. Incidentally, as shown in FIG. 3a, impulsive noise initially has a high peak value and then gradually attenuates, but remains at a level exceeding 0 dBm until a certain time. Therefore, when the level of the signal input to the input terminal 21 exceeds 0 dBm, the touch switch 27 is moved and turns on the contact 27b. Then, the energy charged in the charging circuit 24 is transferred to the diode.
D ₄ and is discharged through contact 27b. As a result, energy is stored in the capacitor C, which increases and decreases as shown in FIG. 3b. Therefore, the threshold detection circuit 28 uses the energy level stored in the capacitor C and a predetermined reference level.
Compared with Vh, the energy level is b in the same figure.
Since the reference level Vh is not reached as shown in FIG. 2, a "0" level signal is output. That is, even if high-level impulsive noise is input, the threshold detection circuit 28 outputs an off-time signal that is not affected by the noise.

On the other hand, when an original regular signal as shown in FIG. energy will not be discharged. As a result, the original signal passes through the filters 22 and 23, and only the positive signal component is taken out by the diode _D1 , and the capacitor C is charged with the positive signal component. Since the energy charged in this charging circuit 24 is not forcibly discharged by the suppressing means 26, it is possible to repeatedly charge and discharge based on the polarity of the signal component and store energy as shown in FIG. 4b. Become. Therefore, the threshold detection circuit 28 uses the charging energy level and the reference voltage.
Vh, but if it is set so that the level when it is an original normal signal is higher than the reference voltage, the threshold detection circuit 28 will accurately output “1” only when it is an original normal signal. A level signal can be output.

Therefore, according to the configuration of the embodiment as described above,
Although the low-pass filter 23 cuts out the low-frequency components of impulsive noise and charges the capacitor C with positive signal components, if high-level impulsive noise is input, the impression switch 27
The energy charged in the capacitor C is suppressed by forcibly discharging it using another discharge system, so it is extracted as a "0" level signal without reaching the reference voltage of the threshold detection circuit 28. This prevents the on-time signal from being erroneously output due to impulsive noise, and can be applied to, for example, a line quality measurement device to obtain a desired line quality measurement signal without malfunction.

Although the above embodiments have been described with respect to the detection of tone signals, it goes without saying that the present invention can be applied to the detection of general signals including impulsive noise. Further, the charging circuit 24 and the discharging circuit 25 are implemented by appropriately varying the charging time constant and the discharging time constant depending on the nature of the input signal, etc. others,
The present invention can be implemented with various modifications without departing from the gist thereof.

(Effects of the Invention) As detailed above, according to the present invention, the original regular signal component can be reliably received without being affected by impulsive noise, and the on-time signal of the original signal can be accurately acquired. It is possible to provide a signal receiving device that can perform

[Brief explanation of the drawing]

FIGS. 1 to 4 are shown to explain one embodiment of the signal detection device according to the present invention.
FIG. 1 is a diagram showing an application example of the device of the present invention, FIG. 2 is a configuration diagram showing a specific example of the signal detection device according to the present invention, and FIGS. 3 and 4 explain the operation of the device of the present invention. The waveform diagrams of FIGS. 5 to 7 are diagrams for explaining the conventional device. 23...Low-pass filter, 24...Charging circuit, 25...
Discharge circuit, 26... Suppression means, 27... Touch switch, 28... Threshold detection circuit.

Claims (1)

[Scope of Claims] 1. A low-pass filter 23 that cuts out low-frequency components of impulsive noise from an input signal that includes a sinusoidal regular signal having a specified signal level and impulsive noise; charging circuits D1, D2, R1, C that charge the low-pass filter output to a grounded capacitor at the other end during a period when the output is a positive signal component;
and a discharge circuit C, R2, D3, R3 that discharges the charging energy of the capacitor during a period in which the output of the low-pass filter is a negative signal component, and a switching circuit is provided between one end of the capacitor and ground. suppression means for forcibly discharging the charging energy of the capacitor by closing the switching circuit in response to high-level impulsive noise exceeding a predetermined level set above the specified signal level among the input signals; 26, a signal receiving device characterized in that it extracts only original normal signal components from the charging circuit.