KR20110064596A - Method and apparatus for removing noise in loop start trunk line ring detection circuit - Google Patents

Abstract

According to the present invention, when a DAA (Data Access Arrangement) is used for a loop start trunk line or a primary side or secondary side insulation circuit is used, a false signal occurs due to a ring signal error in an environment in which electromagnetic wave noise or line electromagnetic wave noise is high. In order to solve the problem of failing to detect the problem, even if the noise component overlaps the ring detection signal, the unnecessary signal is blocked and the valid ring signal is stably detected.

Description

A method and apparatus for removing noise in a loop start trunk line ring detection circuit {APPARATUS AND METHOD FOR REMOVING NOISE IN LOOP-START TRUNK RING DETECTION CIRCUIT}

The present invention relates to a keyphone system, and more particularly, to a method and apparatus for removing noise in a loopstart trunk line ring detection circuit.

Key-Telephone system is a system that can use several phone numbers efficiently as several intercoms are interphone with each phone, and distribute and connect incoming calls. It is mainly composed of the main unit and the telephone, the line connecting the main unit and the telephone, and additional equipment to make the performance of the system more efficient.

The claim is distinguished by the trunk line (the line with the telephone number coming from the telephone station) and the maximum capacity of the system that can accommodate extension subscribers.

A key phone is a phone that is connected to a key phone system to allow interconnection between a trunk line and an extension by operating various function buttons. The type of key phone can also vary depending on whether the main device is digital or analog.

The loop start trunk line circuit of the keyphone exchanger includes a transformer loop start trunk line circuit that has been used for a long time and a data access arrangement (DAA) loop start trunk line circuit that has been frequently used in recent years.

The transformer loop start trunk line circuit has been used to isolate the primary and secondary sides with an impedance matching transformer to isolate the noise of the line, and to detect the ring current with an opto-coupler. In addition, DAA loopstart trunk line circuits are insulated using opto-kappers in integrated circuits, and individual components are housed in chips to dramatically reduce the number of components and are economically implemented.

The transformer loop start trunk line circuit has a large number of components and a large insulated transformer, and also uses a hybrid IC (Integrated Circuit) for relay, DC (Direct Current) voltage current control, and AC (Alternating Current) impedance control. As it takes up a lot of PCB (Printed Circuit Board) space, the circuit material cost is high. For this reason, the DAA loop start trunk line circuit has been popularized, and the DAA loop start trunk line circuit has compensated most of the shortcomings caused by the transformer loop start trunk line circuit, making the circuit implementation very convenient. However, the DAA loop start trunk line circuit has a problem of incorrectly detecting a ring signal because it does not fundamentally block noise of the trunk line by using integrated circuit isolation. Therefore, there is a need for a method for accurately detecting a ring signal even in a noisy environment.

Therefore, in the present invention, when noise and noise are induced in the DAA circuit or the system is not grounded, the noise component overlaps the detection output signal, resulting in a false ring, and sometimes the ring component does not detect the noise. The present invention provides a method and apparatus for removing noise in a DAA loopstart trunk line ring detection circuit capable of blocking unnecessary signals even if overlapped and stably detecting a valid ring signal.

An apparatus according to an embodiment of the present invention is a noise canceling device in a loop start trunk line ring detection circuit, comprising: a DAA loop start trunk line circuit for outputting a trunk line ring detection signal as an analog voltage to a ring terminal (RNG2), and the ring terminal ( And a programmable logic device (PLD) ring validity determination unit configured to block the ring false detection signal caused by the noise by analyzing the analog voltage and frequency output to the RNG2) terminal.

According to an exemplary embodiment of the present invention, a method of removing noise from a loop start trunk line ring detection circuit includes: outputting a trunk line ring detection signal to an RNG2 as an analog voltage, and analyzing the analog voltage and frequency output to the RNG2; Blocking the ring o detection signal caused by the noise.

The present invention can detect a stable ring signal even in an environment where electromagnetic wave noise or line electromagnetic wave noise is high in a loop start trunk line circuit using DAA.

In addition, the present invention can provide a stable call service through the validity of the frequency as well as the voltage of the ring signal.

In addition, the present invention can prevent the ring ringing phenomenon in which the ring does not ring in a situation in which a ring or ring generated by ring signal misdetection occurs even in a condition that power supply ground and communication ground are impossible.

In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Loop-start trunk line circuit of key-phone exchanger receives sinusoidal 80Vrms signal, which is a signaling signal of analog trunk line, analyzes voltage, current or frequency and receives only valid ring signal, and noise from other power or high frequency noise or It is a circuit that determines invalidity of ring error detection due to noise induced in the trunk line and controls stable communication call processing. However, if a DAA (Data Access Arrangement) circuit is used for loop start trunk lines or circuits with unstable primary and secondary insulation, ring signal mis-detection may occur due to ring or signal misconduct in environments with high electromagnetic and electromagnetic noise. The present invention seeks to remedy this problem because it fails to call function.

1 is a configuration diagram of a DAA loop start trunk line circuit.

The tip 107 and ring 109 terminals of the DAA loop start trunk line circuit are input circuits for receiving an 80 Vrms ring signal from the trunk line.

The search circuit (Snoop) 103 cuts the DC voltage by the RC filter, and transfers only the voltage above the threshold voltage to the SNP +/- DAA input terminal by the filter function.

Although not shown in the drawing, the DAA 101 has an internal differential amplifier, and the differential amplifier compares the voltages of SNP + and SNP- with each other and outputs a ring detection signal to RNG2 as an analog voltage. At this time, when a normal ring flows in, the RNG2 terminal output generates a falling pulse whenever the ring voltage crosses 0V. In the case of a 20 Hz, 1 cycle ring signal, two polling pulses are generated. However, without a ring signal, the RNG2 terminal output is maintained at 3.3V.

The inverter 111 inverts the output pulse output from the DAA 101.

The TR integrator generates a voltage of 2V or more during the ring-on time by accumulating the voltage in RC to maintain a pulsed output signal at a constant voltage. If the RNG01 is over 2V by the TR integrating circuit and the ring detection valid timer is satisfied, a call is made and the extension telephone is ringed by the software check. However, if 0V is maintained, the call does not ring because it is not called.

FIG. 2 is a block diagram for determining an effective ring signal in a DAA loop start trunk line circuit according to a first embodiment of the present invention.

In FIG. 2, a primary software (SW) ring validity determining unit (hereinafter referred to as a "primary SW ring validity determining unit") 203 is added to the DAA loop start trunk line circuit shown in FIG. 1.

The RNG01 signal is checked for polling every 10msec by a software timer, and if the voltage is maintained for 360msec, it is determined as a valid ring signal.

3 is a block diagram for determining an effective ring signal in a DAA loop start trunk line circuit according to a second embodiment of the present invention.

FIG. 3 adds a primary PLD ring validity determination unit 305 to the DAA loop start trunk line circuit 201 and the primary SW ring validity determination unit 203 shown in FIG. 2.

The primary PLD validity ring determination unit 305 primarily determines validity. As shown in FIG. 1, the output from RNG2 of the DAA loop start trunk line circuit 101 is transmitted to the primary PLD validity determination unit 305. Thereafter, the primary PLD validity ring determination unit 305 analyzes voltage and frequency with internal logic to block ring false detection due to noise, and then secondarily rings the secondary SW ring validity determination unit 307. Determine the validity.

4 is a flowchart illustrating a valid ring signal determination method in a DAA loopstart trunk line according to the first and second embodiments of the present invention.

Determining a valid ring signal is performed by a controller not shown in the figure. The controller controls the components described in FIGS. 1 to 3.

First, the controller checks RNG01 in step 401. As a result of checking the RNG01, the controller determines whether the voltage of the RNG01 is 2V or more in step 403. Step 403 is a process of determining whether the RNG01 voltage is valid high. If the voltage of RNG01 is not more than 2V, the control unit returns to step 401. However, if the voltage of the RNG01 is 2V or more, the controller increases the counter in step 405 and determines whether the counter value is greater than or equal to 36. If the counter value is less than 36, the control unit returns to step 401. However, if the counter value is greater than or equal to 36, the control unit rings the phone at the rhythm determined in step 407. In step 409, the controller determines whether the user off-hooks the phone. If the user does not off-hook the telephone, the controller returns to step 407. However, when the user off-hooks the telephone, the controller determines whether the user has turned off the telephone by ending the telephone call in step 411. If the user does not turn off the phone, the controller maintains the current state in step 413. However, when the user turns off the phone, the control unit returns to step 401.

5 is a diagram illustrating a step-by-step process of detecting ring o by inflow of noise according to a second embodiment of the present invention.

The waveform shown in the search circuit 501 is an actual waveform in which longitudinal noise of 2.6 Vpp is continuously introduced between the ground and the tip due to the electromagnetic noise. The vertical voltage noise is not blocked in the search circuit 501 and is input to SNP +/− of the DAA loop start trunk line circuit 503. At this time, if the parallel capacitor 30pF is attached to the SNP +/- terminal of the DAA loop start trunk line circuit 503, the noise is bypassed to the ground, and the amount of noise transmitted to the DAA loop start trunk line circuit 503 is reduced, so that the detection range of the RNG2 output ring is reduced. Will be reduced. However, it is not a perfect complement, and because the noise level is variable and the capacitor capacity is increased, the capacitor capacity can no longer be increased because the AC ring signal is also attenuated when a valid ring is introduced.

In RNG2, which is a ring detection output terminal of the DAA loop start trunk line circuit 503, a ring having a width of 3 msec is detected and output every 4 msec. As a result, two to three rings are checked every 10 msec and can be determined as a valid ring.

When the validity of the ring signal is determined using the block diagram for determining the effective ring signal shown in FIG. 2, a false ring phenomenon occurs due to ring o detection. However, when the validity of the ring signal is determined using the block diagram for determining the effective ring signal illustrated in FIG. 3, that is, the validity of the ring signal is determined using the primary PLD ring validity determination unit 505 of FIG. 5. If it is determined, the validity is detected by comparing whether the frequency of 3msec width is 20Hz, so that the signal transmitted to the software is almost eliminated. For example, even if some of the output is transmitted to the secondary SW ring validity determination unit 507 because of no blocking, the probability of detecting a valid signal more than 36 consecutive times every 10 msec is significantly lowered.

6 is a view for explaining a method for determining ring validity using a subtraction counter to which the present invention is applied.

First, the RNG2 output of the DAA loopstart trunk line circuit outputs a polling pulse whenever the ring signal crosses 0V. Therefore, during the ring on time, the 20Hz ring signal outputs a total of 40 pulses with two pulses in one cycle. Therefore, rather than simply counting the number of pulses, a control algorithm can be applied to increase ring detection reliability.

First, when a 20 Hz ring is detected, one cycle becomes 50 msec, and when 3/4 cycles are found, it becomes 37 msec. This is set to the subtraction counter 1 as shown in FIG. If one pulse of one RNG2 is countered before this subtraction counter is terminated, it is determined to be a valid frequency; if there is no pulse counter, the ring frequency is slower than 20 Hz, and if more pulses are countered, it is faster than 20 Hz. If the number is not one, all are treated as invalid rings. If the second subtraction counter 2 is ringed for one second to determine the validity of the ring on period, as shown in FIG. 6B, the second subtraction counter 2 is set to 360 msec in association with the ring detect timer of the key phone system. The pulse must continue to be counted until the counter terminates, indicating a normal ring-on period. If the counter of the RNG2 pulse stops before the counter 2 is finished, it can be judged as noise. In addition, the subtraction counter 3 may be set to be smaller than the ring off time to determine the ring cadence validity. When the pulse of RNG2 is continuously counted and stopped, as shown in (c) of FIG. 6, the counter is down by 1800 msec. If RNG2 is restarted after the counter ends, it can be determined that it is the second ring. In other words, after the subtraction counter 2 is finished, the subtraction counter 3 starts from the point where the RNG2 continues to count. When these three subtraction counters determine the validity of a full wave pulse, noise blocking is possible.

7 is a flowchart illustrating a method of determining ring validity using a subtraction counter according to an embodiment of the present invention.

The control unit receives a ring detect signal from the DAA trunk line circuit 301 in step 701. Sampling the ring burst input to the Ring Detect signal and setting 37msec to 1 subtraction counter 1 when detecting a 20Hz ring.

In step 703, the control unit subtracts the subtraction counter 1, and determines whether the ring burst has been detected twice. If the ring burst is not detected twice, the control unit returns to step 701, and counter noise is detected as well as counter initialization. However, if the ring burst is detected twice, the control unit accumulates the valid counter in step 705. Thereafter, the control unit may return to step 701 after the accumulation and repeat the above operation, or may determine whether the valid counter is greater than 360 msec to determine the ring-on validity in step 707. However, hereinafter, the case where it is determined whether the effective counter is greater than 360 msec will be described. In operation 707, the ring on period reference value is 360 msec. If the valid counter is not greater than 360 msec or the valid counter is 360 msec, the control unit accumulates the ring off valid counter in step 711. After accumulating the ring-off valid counter, if there is no accumulation in the ring-on valid counter even after 1800 msec, the flow returns to step 701.

However, if the valid counter is greater than 360 msec, the control unit accumulates the ring on valid counter in step 709.

After step 707 and step 709, the control unit determines whether the ring on / ring off counter alternates until before the hook-off in step 713.

If the ring-on / ring-off counter alternates until before the hook-off, the controller determines that the ring is a valid ring in step 715. However, if the ring-on / ring-off counter has not been altered before the hook-off, the control returns to step 701, and if the ring-on / ring-off counter stops before the on-hook, the controller initializes validity because the call is canceled on the way. .

The present invention enables stable ring signal detection of a loop start trunk line circuit using DAA in a noisy environment, and enables stable call service by analyzing the validity of the frequency as well as the voltage of the ring signal. In addition, the present invention can provide the stabilization of the call signaling by preventing the ring ring or ringing phenomenon even in the condition that the power ground and communication ground is impossible.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

1 is a configuration diagram of a DAA loop start trunk line circuit,

2 is a block diagram for determining an effective ring signal in a DAA loop start trunk line circuit according to a first embodiment of the present invention;

3 is a block diagram for determining an effective ring signal in a DAA loop start trunk line circuit according to a second embodiment of the present invention;

4 is a flowchart illustrating a valid ring signal determination method in a DAA loop start trunk line circuit according to a first embodiment and a second embodiment of the present invention;

FIG. 5 is a diagram illustrating a step by step process of detecting noise due to inflow of noise according to a second embodiment of the present invention;

6 is a view for explaining a method for determining ring validity using a subtraction counter to which the present invention is applied;

7 is a flowchart illustrating a method of determining ring validity using a subtraction counter according to an embodiment of the present invention.

Claims (4)

A noise canceling device in a loop start trunk line ring detection circuit, DAA (Data Access Arrangement) loop start trunk line circuit which outputs CO line ring detection signal to ring terminal as analog voltage, And a programmable logic device (PLD) ring validity determining unit configured to block the ring false detection signal caused by the noise by analyzing the analog voltage and frequency output to the ring terminal. The method of claim 1, The PLD ring validity judgment unit judges whether a valid non-blocking ring false detection signal is detected 36 or more consecutive times every 10 msec, and the ring false detection signal is valid for 36 consecutive consecutive times every 10 msec. And a software ring validity determining unit to determine a valid ring. A noise removing method in a loop start trunk line ring detection circuit, Outputting the trunk line ring detection signal to the ring terminal as an analog voltage; And blocking the ring false detection signal caused by the noise by analyzing the analog voltage and the frequency output to the ring terminal. The method of claim 3, wherein It is determined whether a valid non-blocking ring false detection signal is detected 36 or more consecutive times every 10 msec, and when the valid ring false detection signal is detected 36 or more consecutively every 10 msec, a valid ring is determined. The noise removing method of the loop start trunk line ring detection circuit further comprising a process.

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