JP2889033B2 - Loop circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loop circuit, and more particularly to a loop circuit for applying a current load to a local line.
This type of loop circuit is provided in a channel interface unit of a subscriber terminal device (telephone, etc.) or a transmission device, and transmits a dial pulse, transmits an off-hook signal at the time of calling or ringing a terminal, and transmits a voice signal to a voice. It has various functions such as bypassing the circuit.

[0002]

2. Description of the Related Art FIG. 6 is a diagram showing a conventional loop circuit, in which 1 is a power supply / monitoring circuit on the station side, 11 is a loop current detector (A), 12 is a transformer, 2 is a ring oscillator, Is a current detection type ring trip circuit, 31 is a low pass filter (LPF), 32 is a differential amplifier circuit (AMP), 33
Is a comparator (CMP), 4 'is a conventional loop circuit on the terminal side, 41 is a diode stack (rectifier circuit), 42
′ Is a current source circuit, and 5 is an audio circuit.

When a calling signal is sent from a station to a terminal, the relay contacts rt ₀ and rt ₁ shown in the figure are picked for, for example, one second,
So as to rest for 2 seconds, intermittently applied ringer voltage _{V R (100V rms, 20H Z} ) to the loop circuit 4 '. When the relay contact rt _0, rt ₁ is not pick, DC-48V is line resistance of the power supply and monitoring circuit 1 R _L
And a current source circuit 42 ′ via a diode stack 41.
Is applied to When the receiver is picked up in this state, the off-hook signal OFH is input to cause the light emitting diode PD to emit light,
To conduct a photo-transistor Q _2. Then, the transistor Q load current I _L of approximately V _ZD / R _e corresponding to the Zener voltage V _ZD of the Zener diode ZD flows to the _1, loop current detector 11 of the feeder and monitoring circuit 1 this load current I
The transmission of the calling signal is stopped by detecting _L.

FIG. 7 illustrates the operation of a conventional loop circuit.
The figure shows the relay contact rt₀, Rt ₁Is picking
The operation timing chart at the time is shown. Relay contact
rt ₀, Rt₁Picks, D is added to the loop circuit 4 '.
Ringer voltage V biased to C-48V_RIs applied
It is. The diode stack 41 rectifies this,
A DC voltage V higher than normal is supplied to the current source circuit 42 '._DCApply
I do. And while the off-hook signal OFH is not input
Load current I_LHardly flows, but the off-hook signal OFH
Is input, the Zener diode ZD
Ener voltage V_ZDThe peak value is approximately V_ZD/ R_eIn kula
Ringer current I as pumped_LFlows.

At this time, the ringer voltage V_RIs DC-48
V, the ringer current I_LTo
Is the time in the direction flowing to + and the direction flowing to-as shown
Imbalance occurs. Resistance R_dIs the ringer current I_L
Is the voltage signal V_dAnd the ring trip circuit 3
, First, the low-pass filter 31 _d
, And after that, the differential amplifier circuit 32
Signal V_dDC component caused by the time imbalance of
Amplify. Then, the comparator 33 outputs the amplified
DC component voltage signal V_DAnd a predetermined threshold voltage V_thCompare with
And the voltage signal V_DIs a predetermined threshold voltage V_thBeyond
Output a ring trip signal RTS
To stop sending.

[0006], DC component caused by the temporal imbalance of the voltage signal V _d is greater the larger the peak value of the ringer current I _L flowing through the line. However, conventionally, even when applying a relatively large ringer voltage V _R to the loop circuit 4', DC-48V from power supply and monitoring circuit 1
Is added to the transistor Q _1.
Was flowing to. For this, not flow a large ringer current I _L to the line, was delayed as a result of the ring trip detection.

[0007]

In conventional loop circuit as described above [0005], even if the application of a ringer voltage V _R,
A large ringer current I _L did not flow through the line, and as a result, the detection of the ring trip was delayed. The purpose of the present invention is
It is an object of the present invention to provide a loop circuit capable of shortening the ring trip detection time on the station side .

[0008]

The above-mentioned problem is solved, for example, by referring to FIG.
Is solved. That is, the loop circuit of the present invention includes a rectifier circuit 41 for rectifying the ringer voltage applied to the central office line, the collector of the transistor Q ₁ is one of the output terminals of the rectifier circuit, and an emitter through a follower resistor R _e the other output terminal of said rectifier circuit, and the base is the constant voltage element ZD between the first bias resistor R _a and the other output terminal between said one output terminal via a switch means SW In a loop circuit including a current source circuit 42 connected to each other, a second bias resistor _Rb is connected in series with the constant voltage element ZD between the switch means and the other output terminal.

[0009]

[Action] In FIG. 1, the rectifier circuit of the loop circuit 4 41 forms a high DC voltage V _DC than usual due to the application of the ringer voltage V _R. Although the current source circuit 42 is powered by the rectification circuit 41 is to form the current load by a predetermined control signal CS, the time, since the ringer voltage V _R is biased in DC-48V, Ringer current the I _L and the direction of flow in the + - temporal imbalance between the flow direction occurring. Then, DC components based on the imbalance is greater the larger the peak value of the ringer current I _L. Therefore, when applying a high voltage, such as Ringer's voltage V _R to the loop circuit 4 is constructed Yo increase the peak value of the load current I _L that flows from the current source circuit 42 to the line, ring trip detection time as a result Is shortened. In the present invention (1)
According, the constant voltage to the self-biasing circuit of the transistor Q ₁
Connected in series with an element (eg, Zener diode ZD)
The configuration provided with the second bias resistor _Rb ,
Higher ringer voltage is supplied and the switch means is O
When it is N, the base bias of the transistor Q ₁
(That is, the magnitude of the ring trip load current flowing through the local line.
) Can be increased at the desired rate, and the
The ring trip detection time is shortened. Also at that time
Is a constant voltage element Z in series with the second bias resistor _Rb.
D, the ring trip load current
The difference in size depends on the distance from the station to the loop circuit.
Instead, it can be kept within a desired range. Moreover,
The ratio of the magnitude of the ring trip load current and the station
Ring trip load depending on distance from the loop circuit
The ratio of the difference in the magnitude of the current is different from the voltage of the constant voltage element ZD.
An appropriate combination with the resistance value of the second bias resistor _Rb is selected.
Can be set as desired. In other words, the transistor Q ₁
When you want to apply the same level of bias to the base
In addition, if the voltage of the constant voltage element ZD is selected to the same level as before.
In this case, the resistance value of the second bias resistor _Rb is selected to be small.
By dividing the load current for ring trip
Ring trig based on the distance from the station to the loop circuit
Of the difference in the magnitude of the
Wear. Also, the voltage of the constant voltage element ZD is selected to be smaller than before.
The resistance value of the second bias resistor _Rb instead.
By selecting a large value, the load current for ring trip can be increased.
And the distance from the station to the loop circuit.
Grip load current
Can be set.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described below in detail with reference to the accompanying drawings. Note that the same reference numerals indicate the same or corresponding parts throughout the drawings. FIG. 2 is a diagram showing a loop circuit of the embodiment, in which 4 is a loop circuit of the embodiment,
41 is a diode stack (rectifier circuit), and 42 is a current source circuit.

The current source circuit 42 of the loop circuit 4 has a resistor _Rb connected in series with the Zener diode ZD at _one of the base bias supply circuits of the transistor Q1.
So, now, the base current I at the time of conduction of transistor Q ₁
When _b is sufficiently small, the base bias voltage V _B of the transistor to Q ₁ when applying a DC voltage V _DC to the current source circuit _{42, V B = R b (V} DC -V ZD) / (R a +
R _b ) + V _ZD . That is, the base bias voltage V _B changes according to the rectified voltage _VDC of the diode stack 41. At this time, the load current I _L flowing through the transistor Q ₁ is given by approximately V _B / _Re , so that this load current I _L is also the rectified voltage V _{DC of the} diode stack 41.
Will change in accordance with

[0012] With this configuration, the station calls the terminal
When sending a signal, use the relay contact rt shown in the figure. ₀, Rt₁For example
Pick for 1 second, pause for 2 seconds, loop
100V for circuit 4_rms, 20H_ZRinger voltage V_RTo
It is applied intermittently. Relay contact rt₀, Rt₁Is pick
Otherwise, the DC-48V of the power supply / monitoring circuit 1
In resistance R_LAnd current through the diode stack 41
It is applied to the source circuit 42. If you pick up the handset in this state,
When the off-hook signal OFH is input, the light emitting diode PD is turned on.
Light emission, phototransistor Q_TwoIs made conductive. Soshi
And transistor Q₁To the power supply / monitoring circuit 1
About V corresponding to DC-48V_B/ R_eLoad current I_LFlow
The loop current detector 11 of the power supply / monitoring circuit 1
Load current I_LTo stop sending the call signal by detecting
You.

FIG. 3 is a diagram for explaining the operation of the loop circuit of the embodiment, and FIG. 3 shows an operation timing chart when the relay contacts rt ₀ and rt ₁ are picking. When the relay contacts rt ₀ and rt ₁ pick, the loop circuit 4
Biased 100 V _rms to C-48V, ringer voltage V _R of 20H _Z is applied. Diode stack 4
1 applies a DC voltage _VDC higher than usual to the current source circuit 42 by rectifying this. And, although while the off-hook signal OFH is no input load current I _L does not flow hardly, if off-hook signal OFH is inputted, large ringer current as the line the wave height value is clamped at substantially V _B / R _e I _L flows.

At this time, the ringer voltage V_RIs DC-48
V, the ringer current I_LTo
Is the time in the direction flowing to + and the direction flowing to-as shown
Imbalance occurs. Resistance R_dIs the ringer current I_L
Is the voltage signal V_dAnd the ring trip circuit 3
, First, the low-pass filter 31 _d
And the differential amplifier circuit 32 removes the voltage signal V_d
Amplifies the DC component caused by the time imbalance of
You. This DC component is the ringer current I_LThe peak value of
Therefore, it is much larger than usual. So
Then, the comparator 33 supplies the amplified DC component with an electric current.
Pressure signal V_DAnd a predetermined threshold voltage V_thAnd comparing the
Voltage signal V_DIs a predetermined threshold voltage V_thWhen exceeds
Outputs grip signal RTS and stops sending call signal
Let it. As a result, the ring trip detection time t is
Has also been shortened.

The resistor _Rb and the Zener diode ZD in FIG. 2 may be exchanged. Figure 4 is a diagram showing a loop circuit of another embodiment, indicia applied to the loop circuit contrary to the above
The magnitude of the ring trip load current is large depending on the applied voltage
It shows the case where it changes sharply. In the drawing, 4 is a loop circuit of another embodiment, 41 is a diode stack, 42 is a current source circuit, 6 is a voltage detection type ring trip circuit, 61
Denotes a low-pass filter amplifier (AMP), and 62 denotes a comparator (CMP).

In the loop circuit 4 of this embodiment,
The flow source circuit 42 has a transistor Q₁Base bias supply
Zener diode ZD connected to the circuit as shown
Resistance R_bAnd Therefore, the current source circuit 42
Current voltage V_DCTransistor Q when voltage is applied₁Baseball
Ias voltage V_BIs V_B= V_DC-V_ZDGiven by Immediately
The base bias voltage V_BIs a diode stack
41 rectified voltage V_DCIt changes according to. Also, at that time
Transistor Q₁Load current I flowing through_LIs approximately V _B/ R_e
, The load current I_LAlso diode star
Rectified voltage V_DCWill change in accordance with

On the other hand, in this example, the voltage detection type
A grip circuit 6 is provided. Therefore, the loop circuit 4
To 100V_rms, 20H_ZRinger voltage V_RAdd
And the peak value of the line is approximately (V_DC-V_ZD) / R_eso
Determined large Ringer current I _LFlows. This ringer
Current I_LFlows in the direction of + and-in the same manner as in FIG.
There is a time imbalance between directions. Resistance R_dBox's
Ringer current I_LIs the voltage signal V_dConvert to And
In the ring trip circuit 6, first, a low-pass filter
Voltage amplifier V_dRemoving the AC component of
The voltage signal V _dD caused by the time imbalance of
Amplify the C component. This DC component is the ringer current I_Lof
It increases as the peak value increases. And con
The parator 62 outputs the amplified DC component voltage signal V_D
And a predetermined threshold voltage V_thAnd the voltage signal V
_DIs a predetermined threshold voltage V_thRing trip when exceeding
The signal RTS is output to stop sending the calling signal. So
As a result, the ring trip detection time t is reduced.

FIG. 5 shows the line resistance of the loop circuit according to the embodiment.
FIG. 4 is a diagram showing constant current characteristics. Conventionally, the load current of a line is fixed at a constant I _Lmax ′, regardless of the size of the line distance, that is, the size of the line resistance _RL . This point, according to the present embodiment, the distance of the line is large, i.e., when the line resistance R _L is applied a relatively high ringer voltage V _R at the time of the large are a ringer current I _Lmax accordingly Can be larger. In addition, the ringer current _ILmax increases as the line distance decreases, that is, as the line resistance _RL decreases. Therefore, the ring trip detection time t is significantly reduced as compared with the related art.

[0019] The transistors Q ₁ in the above embodiment to form a load current I _L mentioned in the case of NPN transistors of the junction type is not limited thereto. Transistor Q ₁ is may be a junction of the PNP transistor, this may be a bias circuit in the opposite case. Further, the transistor Q ₁ in the above embodiment to form a load current I _L mentioned in the case of junction transistor is not limited thereto. Transistor Q ₁
May be a field effect transistor (FET).

[0020]

As described above, according to the present invention, the current source circuit 42 of the loop circuit 4 is connected to the rectified voltage _{VDC of the} rectifier circuit 41.
Which is configured to vary the load current I _L in accordance with, performed much faster ring trip when added ringer voltage V _R to the line.

[Brief description of the drawings]

FIG. 1 is a diagram showing the basic configuration of the present invention.

FIG. 2 is a diagram illustrating a loop circuit according to an embodiment;

FIG. 3 is a diagram illustrating an operation of the loop circuit according to the embodiment;

FIG. 4 is a diagram illustrating a loop circuit according to another embodiment.

FIG. 5 is a diagram showing a line resistance-constant current characteristic of the loop circuit of the example.

FIG. 6 is a diagram showing a conventional loop circuit.

FIG. 7 is a diagram illustrating the operation of a conventional loop circuit.

[Explanation of symbols]

 4 Loop circuit 41 Rectifier circuit 42 Current source circuit

Claims (1)

(57) [Claims] 1. A rectifier circuit for rectifying a ringer voltage applied to a local line, a collector of a transistor connected to one output terminal of the rectifier circuit, and an emitter connected to the other output terminal of the rectifier circuit via a follower resistor. And a current source circuit whose base is connected to a first bias resistor between the one output terminal and a constant voltage element between the first output resistor and the other output terminal via switch means, respectively. A loop circuit comprising a second bias resistor connected in series with the constant voltage element between the switch means and the other output terminal.