KR20040051657A - Ring trip detection apparatus in Subscriber Line Interface - Google Patents

Abstract

PURPOSE: An apparatus for detecting a ring trip in a subscriber line interface is provided to realize a stable SLIC(Subscriber Line Interface Circuit) function by detecting a ring signal applied to a subscribe line before/after subscriber phone is off-hook and preventing ring trip. CONSTITUTION: A low pass filter(231) receives feedback of ring signals applied to a subscriber line(220) for low-pass filtering the ring signals. An analog-to-digital converter(232) converts the filtered ring signals into digital values before and after off-hook of a subscriber telephone. A delay(233) temporarily stores a ring voltage before the off-hook of the subscriber telephone. A comparator(234) compares the ring voltage after the off-hook of the subscriber telephone with the ring voltage before the off-hook of the subscriber telephone stored in the delay(233). If a difference voltage between the ring voltages is larger than a ring trip threshold, the comparator(234) transmits the difference voltage to a main processor(240).

Description

Ring trip detection apparatus in subscriber line interface

The present invention relates to a ring trip detection function that may occur in a subscriber line interface circuit (SLIC) chip used in a general subscriber board, especially when a capacitance value on a line is large. The present invention relates to a ring trip detection device capable of solving the operation.

In general, a ring trip indicates that a ring is ringed on the other party's phone when the subscriber makes a call, and when the ring is ringing, the other party picks up the receiver and recognizes it on the subscriber board.

The ring trip detection apparatus in the conventional subscriber line interface is shown in FIG.

A low pass filter (LPF) 131 for feeding back the ring applied to the subscriber line 120 back into the SLIC chip 130 to convert the alternating portion of the ring into a digital value, and an output from the low pass filter 131. And a SLIC chip 130 including a comparator 132 for outputting a ring trip to the main processor 140 by comparing the difference between the set value and the ring trip detection threshold set by the user. .

The ring trip detection apparatus in the conventional subscriber interface as described above will be described with reference to FIG. 1.

First, when a ring is applied to the subscriber line 120, the ring rings to the subscriber telephone 110. At this time, when the handset of the subscriber telephone 110 is off hooked, the ring is fed back from the line 120 into the SLIC chip 130.

Here, as shown in FIG. 2, the ring voltage of the subscriber telephone and the hook voltage when the hook voltage is in the off hook state are generated.

The inside of the SLIC chip 130 is composed of a low pass filter 131 and a comparator 132 to detect a ring trip. The low pass filter 131 is formed when the ring applied to the line is fed back into the chip. Changes the AC component to DC, compares the DC value output from the low pass filter 131 with the ring trip detection threshold value set by the user, and outputs whether or not the ring trip is detected as a difference value to the main processor 140. Done.

At this time, when the comparison result of the comparator 132 is smaller than the threshold value set by the user it is notified to the main processor 140 of the exchange system as a ring trip detection signal.

However, in the related art, there is a case where the value of the capacitor C on the subscriber line 120 is very large according to the line situation. In this case, the voltage of the ring fed back to the SLIC chip 130 and applied is the value of the capacitor C. It becomes smaller in proportion to. In this case, if the value of the capacitor C is too large, the voltage of the fed back ring becomes smaller than the ring trip detection threshold value even though the subscriber does not off-hook the receiver, and the SLIC chip 130 malfunctions to output the ring trip detection signal. .

The present invention has been made to solve the above problems, and detects a ring signal applied to the subscriber line before and after the off hook of the subscriber telephone, and generates a ring trip detection signal when the detected voltage difference is greater than or equal to the ring trip threshold. It is an object of the present invention to provide a ring trip detection device at a subscriber line interface.

Another feature is that the SLIC chip further includes a delay unit to temporarily store the voltage before the off hook of the subscriber telephone and apply the voltage before and after the off hook to the comparator, so that the ring trip in which the difference between the two voltages is set by the user is set. It is an object of the present invention to provide a ring trip detection device at a subscriber line interface, which is capable of outputting a ring trip detection signal in comparison with a threshold.

1 is a block diagram showing a conventional ring trip detection device.

2 is a feedback ring waveform diagram in a subscriber line interface circuit according to the handset state.

3 is a block diagram illustrating an apparatus for detecting a ring trip at a subscriber line interface according to an exemplary embodiment of the present invention.

4 is a configuration diagram of a delay unit of FIG. 3 of the present invention;

<Description of the symbols for the main parts of the drawings>

210 Subscriber 220 Subscriber Track

230 ... SLIC chip231 ... low pass filter

232 Analog-to-digital converter 233 Delay

234 ... Comparators240 ... Main Processor

Ring trip detection device in a subscriber line interface according to the present invention for achieving the above object,

A low pass filter receiving the ring signal applied to the subscriber line and performing low pass filtering;

An analog / digital converter for converting the ring signal filtered by the low pass filter into a digital value before / after the off hook of the subscriber telephone;

A delay unit for temporarily storing the ring voltage before the off-hook by the analog / digital converter;

And a comparator for comparing the ring voltage after the off hook of the subscriber telephone with the voltage before the off hook stored in the delay unit, and transmitting the difference voltage to the main processor when the difference voltage is equal to or greater than the set ring trip threshold.

Preferably, the delay unit is composed of a plurality of flip-flops, characterized in that for delaying and outputting the ring voltage before the hook-off of the subscriber telephone converted by the analog / digital converter to the comparator.

Hereinafter, with reference to the accompanying drawings as follows.

3 is a block diagram of a ring trip detection circuit inside the SLIC chip 230 according to an embodiment of the present invention.

Referring to FIG. 3, a low pass filter 231 for low pass filtering a ring signal fed back from a subscriber line 220, and an analog / digital converter 232 for converting the low pass filtered ring signal into a digital value. Wow; A delay unit 233 for temporarily storing the output of the analog / digital converter 232; Ring trip detection before and after the hook off from the subscriber is received from the analog / digital converter 232 and the delay unit 233 and compared and the difference voltage is greater than or equal to the detection threshold value. The comparator 234 outputs a signal to the main processor 240.

The delay unit 232 includes a plurality of flip-flops FF1 and FF2 for delaying and outputting a digital value by a clock.

The ring trip detection circuit in the subscriber line interface according to the present invention as described above will be described with reference to the accompanying drawings.

Referring to FIG. 3, the ring signal to the subscriber line 220 rings the phone 210 through the subscriber line 220 and is applied into the SLIC chip 230. At this time, the SLIC chip 230 outputs a ring trip detection signal by using the ring signal before the telephone hooks off and the feedback ring signal when the subscriber picks up the receiver.

To this end, the SLCI chip 230 includes a low pass filter 231, an analog / digital converter 232, a delay unit 233, and a comparator 234. The low pass filter 231 is a ring signal fed back. The low-pass filtering is output to the analog / digital converter 232, and the analog-digital converter 232 converts the ring signal fed back when the ring rings on the subscriber line 220 to a digital value delay unit 233 )

When the subscriber off-hooks the receiver while the ring is ringing, the ring voltage fed back to the SLIC chip 230 suddenly decreases, and the reduced ring voltage is converted into a digital value by the analog / digital converter 232. Is converted and input to the comparator 234.

At this time, the delay unit 233 is composed of two flip-flops (FF1, FF2), as shown in Figure 4, the first feedback flop (Data_in) before the first off-hook on the subscriber line The feedback ring voltage stored in the first flip-flop FF1 when the next clock is off-hook, and stored in the second flip-flop FF2, and then the comparator 234 at the next clock. Will output Here, the delay time of the delay unit 233 can be arbitrarily adjusted.

Then, the comparator 234 compares the difference between the digital value stored in the analog / digital converter 232 and the ring voltage before the off hook previously stored in the delay unit 233. At this time, when the difference value between the two input values is greater than the value larger than the detection threshold value set by the user, the ring trip detection signal is output.

That is, the difference between the ring voltage before the off-hook voltage of the ring applied to the subscriber line 220 and the voltage of the ring when the off-hook is detected, and the ring trip detection signal when the voltage of the detected difference is greater than or equal to the threshold value To the main processor 240 of the exchange system.

As described above, according to the ring trip detection device of the subscriber line interface circuit according to the present invention, the ring trip detection signal is not outputted only by the input feedback ring voltage when the subscriber off-hooks, but when the subscriber does the off-hook. By detecting the difference between the feedback ring voltage as well as the voltage before off-hook and outputting a ring detection signal, a stable SLIC can be prevented by preventing ring trip detection malfunction when the capacitance value on the line of the existing SLIC chips is large. It has the effect of being able to perform a function.

Claims (2)

A low pass filter receiving the ring signal applied to the subscriber line and performing low pass filtering; An analog / digital converter for converting the ring signal filtered by the low pass filter into a digital value before / after the off hook of the subscriber telephone; A delay unit for temporarily storing the ring voltage before the off-hook by the analog / digital converter; A ring trip at the subscriber line interface, comprising a comparator for comparing the ring voltage after the off hook of the subscriber telephone with the voltage before the off hook stored in the delay unit and transferring the difference voltage to the main processor when the difference voltage is greater than or equal to the set ring trip threshold. Detection device. The method of claim 1, And the delay unit comprises a plurality of flip-flops, and delays and outputs the ring voltage before the hook-off of the subscriber telephone converted by the analog / digital converter to a comparator.