JPS587968A - Ringing trip circuit - Google Patents

Abstract

PURPOSE:To reduce malfunctions and to make the circuit small-sized, by detecting how the current value of an AC voltage at the zero crossing time is related to positive and negative thresholds to decide whether a DC current exists of not. CONSTITUTION:Voltage comparators 4 and 8 which compare a current value with positive and negative thresholds respectively are provided, and the presence or absence of a DC current is decided on a basis of the relation between an AC voltage at the zero crossing time and positive and negative thresholds. Thus, even if phases of the voltage and the current are shifted somewhat from each other, malfunctions are not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ring trip circuit for supervising the blocking current of a telephone exchange.

The ring trip circuit detects the presence or absence of speech current, and needs to detect the presence or absence of blood flow speech current superimposed on the alternating current signal of the ring tone.

Conventionally, there have been devices that extract only the DC component using relays or active filters, but it has been difficult to miniaturize these devices. Although many proposals have been made to reduce the size of the device, it has been difficult to reliably detect only the communication current due to the miniaturization.

One of the devices aimed at miniaturization is one that detects the presence or absence of a circulating current based on whether the magnitude of the current flowing at the time of zero cross of the alternating current voltage is greater than a certain value, as shown in FIG.

In Figure 1, 1 is a DC power supply that supplies communication current;
3 is a resistor for current-voltage conversion, 3 is an oscillator for sending a ringing tone,
The voltage comparator 5 which compares the voltage V(2) across the resistor 2 with a certain threshold value (I t A,) of 4 and produces an output 'V4 when s V(21) 1th is obtained is an oscillator. A zero-cross detector detects the time when the transmitter Kai Masuda 3) crosses the cello, 6 is an AND gate, and 7 is an output S-R flip-flop. Here, the threshold value 1th is determined from the DC current value of the detector.

The line impedance and the impedance inside the telephone are connected between A and B, and when the handset (not shown) is hung, no current flows from the DC power source 1, and the transmitter 3
It is only an alternating current.

On the other hand, when the handset is off, the direct current communication current is superimposed on the alternating current.

FIGS. 2A and 2B show the voltage waveforms of various parts when the receiver is on and off the receiver, respectively.

The outputs of the voltage comparator 4 and zero cross detector 5 are set to V
, , V,. The zero cross detector 5 outputs twice during one cycle of the AC component, but the voltage comparator 4
is a hanger for a certain period of time when V(2+ exceeds 1th f).These two outputs 6.V4 are 1th
By setting , there is no time fluctuation in each case, so the output of the ANDKATE 6 is "0" and the Q output of the flip-flop 7 is "]]". Next, when the handset is removed and the DC current from the blood flow power supply 1 is superimposed, the result is as shown in Fig. 2).

The output Vll of the zero cross detector 5 is exactly the same as that shown in Fig. 2 C/1), but the output V4 of the voltage comparator 4 is a superimposed DC current that flows through the current-voltage conversion resistor 2, and the voltage V (
2) changes, so it overlaps with Vll in time.

Therefore, the output of the AND gate B becomes 1" during the overlapping period, the flip-flop 7 is set, the Q output becomes 1, and the DC talking current can be detected.

However, the configuration shown in FIG. 1 causes the following problem. The impedance connected between A and B is
Generally, it is a complex number, and the voltage and current phases do not match,
Malfunction occurs due to current generated by alternating current signals.

The case where the current phase is delayed will be explained with reference to FIGS. 6(a) and β). Figure 3 G4) is the case when the receiver is hung and there is no DC current, but due to the phase shift between voltage and current,
A time occurs when the output 4 of the zero cross detector 5 and the output V of the voltage comparator 4 match in time, the flip-flop 7 is set, and it is erroneously recognized that there is a direct current. In addition, 3rd Np) is a case where the handset is removed and a direct current is superimposed, but the output V of the zero cross detector 5,
There may be times when the output V4 of the voltage comparator 4 does not match in time, and it may be mistaken that there is no direct current.

The present invention was devised in view of the above points, and its purpose is to provide a linogtorinop circuit that can be miniaturized and has fewer malfunctions.

A feature of the present invention is that it has a comparison means that compares the current k (voltage value proportional to the current value) with positive and negative threshold values, respectively, and the current value when the AC voltage is zero chroma is the positive value. - The presence or absence of direct current is determined based on the relationship with a negative threshold.

In other words, the alternating current component is positive and
The purpose is to compare both negative and negative storm flow thresholds and use these two results in making decisions.

Now, the determination result for the positive threshold 1th is DP.

If we compare the determination result according to 11th, Dp=1°Dm-1 is the current due to the alternating current component, and Dp=o.

f) m-1 indicates that there is a direct current. DP-11
IJ) m=0 is an unthinkable state in an ideal state, and if it occurs, it is considered to be due to noise.

Moreover, Dp=o and Dm-o can be considered in either case, and no judgment can be made. These are determined by logic gates as described later.

FIG. 4 shows the configuration of an embodiment of the present invention. Fourth
In the figure, those with the same numbers as in Figure 1 are phased objects.
8 is a threshold value −Ith for detecting the negative current value
9.13 is an inverter, 10 is a D-flip-flop for delaying the output V4 by a half cycle of the AC signal, and 11 and 12 are AND gates.

The operation will be explained with reference to FIG. 5 44) and @l). Fifth
Figure (a) shows the waveform of the main part when the receiver is hung and no direct current is superimposed. In this embodiment, a voltage comparator 8 is provided to detect the current value on the negative side.
When the voltage V(2) exceeds the threshold value -1th to the negative side, an output V is produced. Zero cross detector5. voltage comparator 4,
8 and Antogame) 11.12 outputs are respectively 5th
6°F4, Vs, In, V120) in Figure (A)
(: (!: < f, K'), '11 + '+
Since 2 and 6d"o", the flip-flop 7 remains in its initial state. (In the initial state, flip-flop 7
is reset so that the Q output becomes 0''. Therefore, it is determined that no DC current is flowing. At this time, the outputs of the zero cross detector 51 and the heavy pressure comparator 4 are V, , V.

An overlap occurs, and the output V8 of the voltage comparator 8 is "0". Therefore, the output V8 is inverted to "1" by the inverter 9I, and the output V4 is the output V4.
, is sent to the D-flip-flop 10 by the signal via the inverter 3 and becomes ul''. Therefore, 7
When 7 and V4 overlap for the first time, D-flip-flop 10 is 0'', but when V4 and 7 overlap for the second time, D-flip-flop 10 is 1', As a result, an output VI1 is generated from the AND gate 11, the flip-flop 7 is set, and it is determined that direct current is flowing.

Next, Figure 6 (
4. Shown in (c). Figure 6 3) shows the case where the receiver is hung and there is no direct current, and as shown in the figure, only the output V1□ of the at gate 12 is generated and the flip-flop 7
maintains the "0" state. Figure 6 CB) is the case when the handset is disconnected and direct current is flowing, and as shown in the figure, the output "11" of the AND gate 11 becomes 11. , F'J The block flop 7 is set and becomes "1" to detect direct current and prevent false detection.

As described above, the present invention has a comparison means that compares the current value with the positive and negative threshold values respectively, and it is possible to determine what relationship the current value when the AC voltage crosses with respect to the threshold value of each regular member. Since the presence or absence of a direct current is determined based on whether there is a direct current, there will be no malfunction even if the voltage and current are slightly out of phase.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a conventional embodiment, Fig. 2 is a waveform diagram of the main parts for viewing the operation in Fig. 1, and Fig. 3 is a diagram of the gamma component that explains the malfunction of Fig. 1. FIG. 4 is a diagram showing the configuration of an embodiment of the present invention, and FIGS. 5 and 6 are waveform diagrams of the main parts for explaining the operation of FIG. 4. 3: Transmitter 4, 8: *Pressure comparator 5; Zero cross detector 7: Flip-flop 9.13: Inverter
Tar 11.12: ANDGATE Patent Attorney Bo 1) Riju No. 10 West Diagram 2 (A)

Claims (1)

[Claims] A link trip circuit that monitors the communication current of telephone exchange equipment (herein, a zero volt detection means detects the point in time when the AC voltage becomes zero volts, and a current value is compared with positive and negative thresholds respectively, and a threshold value is determined). It has first and second comparison means that generate an output when the absolute value exceeds the value, and determines the presence or absence of DC current based on the output of the first and second comparison means at the zero-crossing point. A ring trip circuit characterized by the following characteristics.