JPH04196653A - Ring trip circuit - Google Patents

Abstract

PURPOSE:To eliminate erroneous detection by ignoring the detected signal when a ring trip signal disappears during a first guarding time and ignoring the ring trip detection signal while a second guarding time started by an immunity detection signal is continued. CONSTITUTION:A first invalidating means 105 is activated by the ring trip detection signal and the first guarding time T1 is started, during this time the ring trip detection signal is ignored when the ring trip detection signal of a ring trip detection circuit 103 disappears. Also a second ignoring means 106 is provided with the immunity detection signal from an immunity detection circuit 104, by which a second guarding time T2 is started. Then the ring trip detection signal of the ring trip detection circuit 103 is ignored while the second guarding time T2 is continued. Thus adjustment by volume is eliminated and the erroneous detections caused by temperature variation as well as change with the lapse of time are prevented.

Description

[Detailed Description of the Invention] [Summary] Regarding ring trip circuits installed in subscriber digital transmission terminal equipment, etc., there is no need to adjust the volume, and false detection does not occur due to temperature fluctuations or changes over time. In order to improve reliability in this way, a voltage detection circuit detects the voltage across the ringer sending resistor, and a ring trip detection circuit compares the detected voltage of the voltage detection circuit with a predetermined first threshold. A ring trip detection circuit that outputs a signal, an immunity detection circuit that compares the detection voltage of the voltage detection circuit with a predetermined second threshold value and outputs an immunity detection signal, and a ring trip detection signal of the ring trip detection circuit. a first ignoring means that activates a first guard time and ignores the ring trip detection signal when the ring trip detection signal of the ring trip detection circuit disappears during that time; A second ignoring means is provided for activating the second guard time and ignoring the ring trip detection signal of the ring trip detection circuit while the second guard time continues.

[Industrial Application Field] The present invention relates to a ring trip circuit provided in a subscriber system digital transmission terminal equipment or the like.

In digital subscriber circuits, the ringer (
A ring trip function is required to detect the called party's response to this ringer when the ringing signal is sent. The ring trip function is not sensitive to the ringer's alternating current (approximately 16 Hz to 20 Hz) and detects the DC loop voltage when the called party answers, but depending on the system in which this ring trip circuit is used, In some cases, a non-detection condition is set, and when this non-detection condition exists, it is necessary to prohibit ring trip detection.The non-detection condition includes a 200Ω DC loop that continues for 12m5, and a telephone or 5 units connected in parallel (isometrically 1
There is a case where a parallel connection circuit of Ω and 8UF is connected to the telephone side.

Therefore, the ring trip circuit is required to have a function that can detect ring trips and reliably prohibit ring trip detection under non-detection conditions.

[Prior Art] A conventional example of a ring trip circuit is shown in FIG. In the figure, 20 is a circuit that realizes the functions of so-called B, S, D, H, etc., including a power supply circuit, etc., one of which is connected to the switch circuit network of the digital exchange, and the other is the relay contact 10.
and is connected to the telephone set 3 via the subscriber line 11. 1 is a calling signal generator, -48V DC voltage source and 20Hz
It consists of a series circuit of alternating current sources that generates a ringing signal. The calling signal from the calling signal generator 1 is transmitted to the telephone 3 via a ringer sending resistor 2 and further via a relay contact 1o.
added to.

The voltage across the ringer sending resistor 2 is input to the detector 21 via the reduction filter 4 . The detector 21 includes a photocoupler, and the magnitude of the input current of the photocoupler can be adjusted using an adjustment volume 23. The detection output of the detector 21 is input to the microprocessor 22, and the microprocessor 22 determines whether there is a ring trip.

In this conventional ring trip circuit, a ring signal is sent from a ring signal generator 1 to a telephone 3, and when the telephone 3 is off-hook in response, the telephone 3 is connected to a relay contact 1.
0, a DC loop including the ringer sending resistor 2 and the calling signal generator 1 is formed, whereby a direct current flows through the ringer sending resistor 2, and the DC current is transmitted to the detector 21 via the reduction filter 4. A ring trip is determined by detecting it and transmitting it to the microprocessor 22.

[Problems to be Solved by the Invention] A conventional ring trip circuit uses a photocoupler to detect direct current. However, the DC transmissibility (CTR) of a photocoupler varies greatly among individual elements, and in order to set the above-mentioned non-detection condition, it is necessary to adjust the input current of the photocoupler with strict accuracy using the volume 23. However, the adjustment required a lot of effort and time.

Further, the CTR of the photocoupler is subject to large temperature fluctuations and changes over time, so even if the volume 23 is adjusted with strict accuracy, false detection is likely to occur due to temperature fluctuations and changes over time, resulting in reliability problems.

The present invention has been made in view of the above circumstances, and its purpose is to eliminate the need for volume adjustment and to increase reliability by preventing false detections from occurring due to temperature fluctuations and changes over time. There is a particular thing.

“Means to solve problems” FIG. 1 is a diagram explaining the principle of the present invention.

The ring trip circuit according to the present invention includes a voltage detection circuit 102 that detects the voltage across the ringer sending resistor 101;
A ring trip detection circuit 103 compares the detected voltage of the voltage detection circuit 102 with a predetermined first threshold value and outputs a ring trip detection signal, and compares the detected voltage of the voltage detection circuit 102 with a predetermined second threshold value. The immunity detection circuit 104 outputs an immunity detection signal by comparing with the ring trip detection circuit 103, and the first guard time T1 is activated by the ring trip detection signal of the ring trip detection circuit 103. a first ignoring means 105 that ignores the ring trip detection signal when the detection signal disappears; and an immunity detection circuit 10.
The second guard time T is determined by the immi-unity detection signal of 4.
2 and ignores the ring trip detection signal of the ring trip detection circuit 103 while the second guard time T2 continues.

[Operation 1] The operation of the ring trip circuit according to the present invention will be explained below with reference to FIG.

A ring signal is sent from a ring signal generator to a telephone,
When the telephone is not off-hook yet, the detection voltage of voltage detection circuit 102 does not exceed the first threshold, so ring trip detection circuit 103 does not output a ring trip detection signal.

In this case, the load on the phone side is 5 units connected in parallel (1
If the non-detection condition is (parallel circuit of 0Ω and 8uF), the detection voltage becomes large and the ring trip detection circuit 103 outputs a ring trip detection signal. In this case, the second threshold value of the immunity detection circuit 104 is also exceeded, and an immunity detection signal as shown in FIG. 2(a) is output. The second ignoring means 106 is activated, for example, at the falling edge of this immunity detection signal, and is activated at the second guard time T2.
Start. In this case, the second guard time T2 is restarted by inputting the next immunity detection signal before it ends, so the second guard time T2 continues without interruption. This second ignoring means 10
6, the ring trip detection signal is ignored while the second guard time T2 continues, so no ring trip is detected under the above-mentioned non-detection condition.

When the telephone goes off-hook, the ring trip detection circuit 103 outputs a ring trip detection signal.

The signal detected by the ring trip detection circuit 103 is 200
If the signal is under the non-detection condition of Ω and 12 mS, the ring trip detection circuit 103 outputs a ring trip detection signal as shown in FIG. 2(b). In this case, the first guard time TI of the first ignoring means 105 starts when the ring trip detection signal falls, for example. The above-mentioned non-detection condition signal is detected by this first guard time T.
Since it disappears during the period of 1, the 1 non-but trip detection signal under this non-detection condition is ignored by the first ignore signal 105.

On the other hand, during normal off-hook, which is not a non-detection condition, the ring trip detection circuit 103 continues to output the ring trip detection signal even after the first guard time T1 ends, as shown in FIG. 2(c). First ignoring means 10
5, the ring trip detection is performed normally in this case.

At this off-hook time, a DC component is added to the detection voltage of the voltage detection circuit 102 due to the off-hook, so that the second threshold value of the immunity detection circuit 104 is not exceeded, and therefore the second ignoring means 106 is activated. do not have.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 shows a ring trip circuit as an embodiment of the present invention. In the figure, a ringing signal generator 1, a ringer sending resistor 2, a telephone 3, a relay contact 10, a subscriber line 11
, the power supply circuit, etc. 10 are the same as those explained in FIG.

The voltage across the ringer sending resistor 2 is input to a subtracter 5 via a reduction filter 4 . Subtractor 5 is reduction filter 4
The voltage across the ringer sending resistor 2 is extracted while being attenuated, and the detected voltage is input to the amplifier 6 and amplified to a desired magnitude. The output voltage of the amplifier 6 is input to a buffer 7 for generating a ringer trip detection signal and a detector 8 for generating an immunity detection signal.

The buffer 7 consists of an inverted output type comparison circuit, and has a predetermined positive threshold voltage Vl(
For example, 2.5V) is compared with the input voltage, and when the input voltage is lower than the threshold voltage ■1, it outputs "H", and when it is higher than Vl, it outputs "L" indicating ring trip detection. compares the input voltage with a predetermined negative threshold voltage −■2 determined according to the non-detection condition, and when the input voltage is higher than the threshold voltage −■2, H″′ is lower than −V2. At times, it outputs "L".

The ring trip detection signal from the buffer 7 and the immunity detection signal from the detector 8 are input to the microprocessor 9. The microprocessor 9 determines ring trip detection based on these signals, taking into account the non-pressure testing conditions.

The operation of the embodiment circuit will be described below with reference to FIGS. 4 to 6. Here, FIG. 4 is a time chart of the signals of each part of the embodiment circuit when the telephone 3 is on-hook, FIG. 5 is a time chart of the signals of each part of the embodiment circuit when the telephone 3 is off-hook, and FIG.
The figure is a time chart of signals of various parts of the embodiment circuit under the non-detection condition of a load of 10 to 8 μF.

First, to explain the operation when the telephone 3 is on-hook for sending out a ringing signal, a DC loop is not formed at this time, and the voltage across the ringer sending resistor 2 does not include a DC component. At this time, the reduction filter 4, the subtractor 5
As shown in FIG. 4(a), the output voltage amplified by the amplifier 6 becomes only an alternating current component with a small amplitude. Since this AC signal is lower than the threshold voltage 1 of the buffer 7 and higher than the threshold voltage -72 of the detector 8, the buffer 7 outputs an H'' output signal, and the detector 8 outputs an H'' output signal. Since the output signal from the buffer 7 is H'', the microprocessor 9 determines that the ring trip has not yet occurred.

When the telephone 3 is on-hook, if the telephone 3 side is in a non-detection condition with five telephones connected (10Ω 8μF), the output voltage of the amplifier 6 will be as shown in Fig. 6(a). In this case, part of the output voltage exceeds the threshold voltage (2) of the buffer 7, and part of the output voltage exceeds the threshold voltage (2) of the detector 8. As a result, the output signal of the buffer 7 and the output signal of the detector 8 become rectangular waves as shown in FIGS. 6(b) and 6(c), respectively, and these are input to the microprocessor 9.

The microprocessor 9 starts counting the guard time T2 at the fall of the immunity detection signal from the detector 8, and if the next fall of the immunity detection signal arrives before the end of this guard time T2, the guard time is counted. T
Restart the count of 2. This guard time T is determined based on the frequency of the calling signal of 20 Hz, and in this case, a value of 50 m5 plus a certain margin is selected. Therefore, under the above-mentioned non-detection condition, the immunity detection signal only falls every 50 m5, so the guard time T2 continues without interruption. While the guard time T2 continues, the microprocessor 9 ignores the ring trip detection signal from the buffer 7 and does not make a ring trip detection determination.

When the telephone 3 is taken off-hook, the detected voltage of the amplifier 6 becomes a DC voltage component superimposed on an AC component, as shown in FIG. On the other hand, the threshold voltage of the detector 8 is always -2 or higher. For this reason, the detector 8
The output signal of is always ``H'''', so the guard time T2 in the microprocessor 9 never continues.Therefore, the ring trip detection signal "L" from the buffer 7 determines that a ring trip has been detected.

The microprocessor 9 starts counting the guard time TI at the fall of the ring trip detection signal from the buffer 7, and ignores the ring trip detection signal input at the beginning of the guard time T1. This guard time T1 is 5 like the aforementioned guard time T1.
It is chosen as 0m5 plus a certain value, and therefore,
During a normal off-footer, as shown in FIG.
In the non-detection condition when the Ω/12m5 signal is input, the ring trip detection signal or °゛H is input after guard time T1.
Therefore, this non-detection condition will not be erroneously determined as ring trip detection.

[Effects of the Invention] As explained above, according to the present invention, there is no need to adjust the volume, and there is very little variation in characteristics due to temperature fluctuations or changes over time, and false detections due to these are eliminated. This increases reliability.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention; FIG. 2 is a diagram explaining the operation of a ring trip circuit according to the present invention; FIG. 3 is a block diagram showing a ring trip circuit as an embodiment of the present invention; The figure is a time chart of the signals of each part when the example circuit is on-hook, Figure 5 is the time chart of the signals of each part when the example circuit is off-hook, and Figure 6 is the time chart of the signals of each part when the example circuit is off-hook.
Section 7 is a block diagram showing a conventional example of a ring trip circuit. In the figure, 1... Calling signal generator 2... Ringer sending resistor 3... Telephone 4... - Reduction filter 5 - Subtractor 6... - Amplifier 7... Buffer 8 ...Detector 9...Microprocessor 10...Relay contact 11...Subscriber line 20-...Power supply circuit, etc. Tiger 1 according to the present invention I! Explanatory diagram Figure 1 Operation explanatory diagram 4 Ri-8 Lower

Claims (1)

[Claims] 1. A voltage detection circuit (102) that detects the voltage across the ringer sending resistor (101), and a voltage detection circuit that compares the detected voltage of the voltage detection circuit with a predetermined first threshold. a ring trip detection circuit (103) that outputs a ring trip detection signal; an immunity detection circuit (104) that compares the detected voltage of the voltage detection circuit with a predetermined second threshold and outputs an immunity detection signal; A first guard time activated by the ring trip detection signal of the ring trip detection circuit to start a first guard time and ignore the ring trip detection signal if the ring trip detection signal of the ring trip detection circuit disappears during that time.
a second guard time is activated by the immunity detection signal of the immunity detection circuit, and while the second guard time continues, the ring trip detection signal of the ring trip detection circuit is activated. Second ignoring means (106)
and a ring trip detection circuit.