JP3139185B2 - Sensor circuit for telephone line and its unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor circuit for a telephone line provided in a network control unit (NCU: network control device at the lowest layer of the telephone network) and its unit.

[0002]

2. Description of the Related Art FIG. 4 shows a configuration of an NCU using a conventional telephone line sensor circuit. In the figure,
2, 4 are terminals connected to the exchange of the central office, and 6, 8 are relay switches. The relay switches 6, 8 have movable contacts 6a, 8a, respectively. Movable contacts 6a, 8
a is connected to terminal 2 via telephone lines 10 and 12, respectively.
4 is connected. The relay switches 6, 8 also have individual contacts 6b, 6c; 8b, 8c, respectively.
One of the individual contacts 6b, 8b is connected to the primary winding 14a of the line transformer 14. The other individual contact 6
c and 8c are connected to the tone extraction circuit 16, respectively. The tone extraction circuit 16 includes a capacitor 18 and a tone extraction transformer 20.

The secondary winding 14b of the line transformer 14
Are connected to a 2-wire / 4-wire (2W / 4W) conversion circuit 22. The two-wire / four-wire conversion circuit 22 includes the line transformer 1
The two telephone lines on the secondary winding 14b side of
The signal is converted to a line and connected to a signal processing circuit 24 for transmission of an electronic device, for example, a facsimile. Tone extraction circuit 1
6 is connected to a signal processing circuit 24 in the facsimile.

[0004] The signal processing circuit 24 is connected to the telephone lines 10 and 12.
It is determined whether the electric signal flowing through the mobile terminal 6a or 8a is connected to the terminals 26 and 28 or the facsimile side. When the movable contacts 6a and 8a are determined to be connected to the telephone, the individual contacts 6c are determined. , 8c side, and when the facsimile side, switches to the individual contacts 6b, 8b side.

A line current monitoring circuit 30 is inserted into one telephone line 12. The line current monitoring circuit 30 includes a pair of photocouplers 32 and 34. One of the photocouplers 32 receives a light emitting element 32a that emits light when a line current flows in the direction of arrow a, and receives light emitted from the light emitting element 32a. The other photocoupler 34 includes a light emitting element 34a that emits light when a line current flows in the direction of arrow b, and a light receiving element 34b that receives light emitted from the light emitting element 34a. ing.

The outputs of the light receiving elements 32b and 34b are output to terminals 36 and 38, respectively.
Reference numerals 6 and 38 are connected to a hook switch on / off detection circuit and a signal processing circuit 24 of the telephone. When using a telephone or facsimile, the telephone lines 10, 12
A line current, which is a DC component, flows through the circuit. Now, when the line current flows in the direction of arrow a of the telephone line 12, the light emitting element 32
a emits light, and the emitted light is received by the light receiving element 32b, and the received light output is given to the signal processing circuit 24 via the terminal 36.

Further, when the line current flows in the direction of arrow b, the light emitting element 34a emits light, and the light emission is received by the light receiving element 34b. A tone signal such as CNG or DTMF as an AC component is superimposed on the line current as the DC component, and the tone extraction circuit 16 extracts the tone signal from the line current.

[0008]

The telephone line sensor circuit in the NCU having this configuration is such that the tone extraction circuit 16
It has a large and expensive electronic component for extracting a tone 20 and a line current monitoring circuit 3
0 is composed of the photocouplers 32 and 34, and when each is assembled on a mounting board, a considerably large space is required for the assembling.
There is a problem that U becomes large.

The present applicant has inserted a detection coil into the telephone line 12 on June 15, 1992 in order to solve the problem of such a conventional telephone line sensor circuit. The magnitude of the line current and the polarity of the line current are magnetically detected by the detection coil, and the line current is detected from the induced magnetic field from the detection coil using a magnetic sensor such as a Hall element. An application has been made for a telephone line sensor circuit and its unit that does not use a photocoupler and does not require the use of a tone extraction transformer.

The present invention is intended to further improve such a telephone line sensor circuit and its unit filed by the present applicant, and solves the problems of the conventional telephone line sensor circuit shown in FIG. It is another object of the present invention to provide a telephone line sensor circuit and its unit capable of detecting line current with high accuracy.

[0011]

To achieve the above object, a telephone line sensor circuit according to claim 1 of the present invention comprises a line current detecting means for detecting a line current in a telephone line, A first amplifier for amplifying the detection signal detected by the line current detecting means, a second amplifier for further amplifying the output signal of the first amplifier, and a line current based on the output signal of the second amplifier. A comparator for generating a monitor signal; and a tone extraction circuit for extracting a tone signal from an output signal of the first amplifier.

A telephone line sensor unit according to a second aspect of the present invention is characterized in that the telephone line sensor circuit according to the first aspect is provided in the same unit.

In the telephone line sensor unit according to a third aspect of the present invention, the output signal amplified by the first amplifier in the telephone line sensor unit according to the second aspect is output without passing through the tone extracting means. It is characterized by being taken out to the outside.

[0014]

According to the first aspect, since the detection signal detected by the line current detecting means is amplified by the first amplifier and the second amplifier, a change in the detection signal detected by the line current detecting means is small. However, the change in the amplified output becomes large, and the comparator at the subsequent stage of the second amplifier changes the detection signal,
That is, a change in line current can be monitored with high accuracy.

Further, by providing a first amplifier and a second amplifier to monitor a change in line current,
In the first amplifier, a detection signal corresponding to the line current detected by the line current detecting means can be amplified and output within the dynamic range of the first amplifier, and is superimposed on the line current. First tone signal
Can be reliably extracted in the tone extraction circuit at the subsequent stage of the amplifier.

According to the second and third aspects, a telephone line sensor unit capable of monitoring a change in line current with high accuracy and reliably extracting a tone signal is provided.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a circuit diagram of an NCU using a telephone line sensor circuit according to an embodiment of the present invention. Parts and components corresponding to those of FIG. The detailed description of the parts and components having the same reference numerals is omitted here.

The sensor circuit for a telephone line according to the present embodiment includes a detection coil 42 and a magnetic sensor 44 constituting a line current detecting means 40, and first and second amplifying detection signals detected by the line current detecting means 40. Amplifiers 46 and 48,
A comparator 50 for generating a line current monitoring signal from the output signal of the second amplifier 48; a tone extraction circuit 52 for extracting a tone signal from the output signal of the first amplifier 46; and an output signal of the first amplifier 46 And a CI detection circuit 54 for detecting or extracting a call signal from the same unit 60.

The detection coil 42 is connected to the telephone line 12
The magnetic sensor 4 generates a magnetic field according to the magnitude of the line current flowing therethrough and the polarity of the line current.
Numeral 4 comprises a Hall element, for example, and outputs a detection signal according to the magnitude and polarity of the line current from the induced magnetic field of the detection coil 42.

The first amplifier 46 is composed of, for example, a differential amplifier, and amplifies the output from each output unit 44a, 44b of the magnetic sensor. The magnetic sensor 44 generates a predetermined output between the output units 44a and 44b according to the line current flowing in the direction of the arrow a (one polarity) and the direction of the arrow b (the other polarity) in the figure.

The first amplifier 46 has an output characteristic as shown in FIG. That is, when the line current is represented by the horizontal axis and the amplified output is represented by the vertical axis, the minimum to maximum value of the line current (for example, -100 mA to +100 mA)
Has the characteristic that the output of the first amplifier 46 corresponding to the above-mentioned value falls within the dynamic range of the first amplifier.

The first amplifier 46 outputs the output signal directly to the second amplifier 48 and outputs the output signal to the tone extraction circuit 52 and the CI detection circuit 54 via the DC blocking capacitor 51.

The second amplifier 48 is a differential amplifier like the first amplifier 46, but has an output characteristic different from that of the first amplifier 46 as shown in FIG. That is, when the line current is represented on the horizontal axis and the amplified output is represented on the vertical axis, as in FIG. 1
Of the amplifier 46 has a larger value than that of the amplifier 46.

The output characteristics of the second amplifier 48 shown in FIG. 3 indicate that the level of the signal output from the second amplifier 48 is higher than the level of the signal input thereto. It's just that. Therefore, if only a signal having the same level as the output of the second amplifier 48 is to be obtained, it is not always necessary to provide two amplifiers as in this embodiment, and only one amplifier may be used. However, when a single-stage amplifier obtains a signal of the same level as the output of the second amplifier 48 of this embodiment, an amplified output corresponding to a wide range of line current cannot be within the dynamic range of the amplifier. Will be. That is,
A part of the minimum value and the maximum value of the line current is clipped. As a result, the waveform of the tone signal superimposed on the line current is distorted, and it is impossible to reliably extract the tone signal in the tone extraction circuit. It becomes possible.

In the present invention, since at least two amplifiers are provided as in this embodiment, even if the change in the detection signal detected by the line current detecting means 40 is small, the change in the amplified output becomes large. The comparison operation in the comparator 50 at the subsequent stage can be performed with high accuracy, thereby improving the monitoring accuracy of the line current. By providing at least two amplifiers in this manner, the first amplifier 4
Since the amplified output of 6 does not need to be particularly large,
A detection signal corresponding to a wide range of line current detected by the line current detection means 40 can be amplified and output within the dynamic range of the first amplifier, and a tone signal superimposed on the line current can be output. No distortion is caused in the waveform of. Therefore, this first
By extracting a tone signal from the output signal of the amplifier 46, the tone signal can be reliably extracted.

The comparator 50 compares the output signal of the second amplifier 48 with the reference values V1 and V2, and outputs the result of the magnitude comparison to the signal processing circuit 24 via the terminals 36 and 38. Since the second amplifier 48 provides an amplified output that greatly changes even with a slight change in line current, the accuracy of the comparison operation is improved with respect to the setting of the reference values V1 and V2. The output of the comparator 50 is used for detecting the off-hook of the receiver or calculating the telephone charge.

The tone extraction circuit 52 is composed of an amplifier such as an operational amplifier and filters of a type such as a band-pass filter and a low-pass filter connected in this order. The DC blocking capacitor 51 blocks DC from the output of the first amplifier 46. Then, the output is amplified by an amplifier, and then the noise in the output is removed by a filter. Tone extraction circuit 5
The connection order of the amplifier and the filter constituting the second element 2 may be reversed. This filter has a function as a filter for extracting a specific tone, in addition to the noise removing function. The output of the tone extraction circuit 52 is supplied to the signal processing circuit 24 via a terminal 56. The output of the CI detection circuit 54 is also supplied to the signal processing circuit 24 via the terminal 58. The signal processing circuit 24 processes the line current from the outputs appearing at the terminals 36 and 38, the tone signal from the tone extraction circuit 52 supplied via the terminal 56, and the CI detection signal supplied via the terminal 58. In the case of a telephone, the movable contacts 6a, 8a of the relay switches 6, 8 are changed to the individual contacts 6c, 8 according to the signal.
For the electronic device, the movable contacts 6a and 8a of the relay switches 6 and 8 are switched to the individual contacts 6b and 8b, respectively.

In the above embodiment, two stages of amplifiers are provided between the line current detecting means 40 and the comparator 50. However, the number of amplifiers between the stages may be three or more. Further, the tone extraction circuit 52 includes a detection coil 42 and a magnetic sensor 44 constituting the line current detection means 40, first and second amplifiers 46 and 48, a comparator 50 for generating a line current monitoring signal, and the like. Although provided in the same unit 60, the tone extraction circuit 52 may be provided outside the unit 60. When the tone extraction circuit 52 is provided outside the unit 60 as described above, the output from the DC blocking capacitor 51 is directly connected to the terminal 56 of the unit 60 inside the unit 60,
The tone extraction circuit 52 outside the unit 60 is connected to this terminal 56.

Further, the DC blocking capacitor 51 may be provided outside the unit 60. In this case, the DC blocking capacitor 51 and the tone extracting circuit 52 are connected to the terminal 56 outside the unit 60. In such a case, the terminal 56 can be used for the purpose of measuring the state of the signal output from the first amplifier 46 and the like.

Further, the CI detecting circuit 54 may be provided outside the unit 60 similarly to the tone extracting circuit 52, and furthermore, the output of the first amplifier 46 may be changed as in the above-described embodiment. Instead of using it, it may be constituted by completely different means. Further, the CI detection circuit 54 can be omitted at all.

[0032]

As is apparent from the above description, according to the first aspect of the present invention, a conventional tone extracting transformer is not required, so that the size of the NCU can be reduced and the line current can be reduced. Since the detection signal output from the detection means is amplified by the first amplifier and the second amplifier, even if the change in the line current is small, the change in the amplified output becomes large. In this case, the change of the line current can be monitored with high accuracy. Further, since the output of the first amplifier is input to the tone extraction circuit, the tone signal can be reliably extracted.

According to the second and third aspects of the present invention, a telephone line sensor unit capable of monitoring line current with high accuracy and reliably extracting a tone signal can be constructed, and the NCU can be downsized. This allows the NCU to be assembled efficiently.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an NCU using a telephone line sensor circuit according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating output characteristics of a first amplifier according to the embodiment.

FIG. 3 is a diagram illustrating output characteristics of a second amplifier in the embodiment.

FIG. 4 shows a conventional N-type sensor circuit using a telephone line sensor circuit.
It is a circuit diagram of CU.

[Explanation of symbols]

 6, 8 relay switch 10, 12 telephone line 14 line transformer 24 signal processing circuit 40 line current detection means 42 detection coil 44 magnetic sensor 46 first amplifier 48 second amplifier 50 comparison Unit 52: Tone extraction circuit 60: Sensor unit

Continuation of front page (56) References JP-A-5-183651 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04M 1/00 H04M 1/24-1/253 H04M 1 / 58-1/62 H04M 1/66-1/82 H04M 3/02-3/06 H04M 11/00-11/10 H04M 19/00-19/08

Claims (3)

(57) [Claims] A line current detecting means for detecting a line current in a telephone line, and a first amplifier for amplifying a detection signal detected by the line current detecting means. 46); a second amplifier (48) for further amplifying the output signal of the first amplifier (46); and a comparator for generating a line current monitoring signal from the output signal of the second amplifier (48). (50) and a tone extraction circuit (52) for extracting a tone signal from an output signal of the first amplifier (46). 2. A line current detecting means for detecting a line current in a telephone line, and a first amplifier for amplifying a detection signal detected by the line current detecting means. 46); a second amplifier (48) for further amplifying the output signal of the first amplifier (46); and a comparator for generating a line current monitoring signal from the output signal of the second amplifier (48). (50) A sensor unit for a telephone line, comprising: a tone extraction circuit (52) for extracting a tone signal from an output signal of the first amplifier (46). 3. A line current detecting means (40) for detecting a line current in a telephone line (10, 12), and a first amplifier (A) for amplifying a detection signal detected by the line current detecting means (40). 46); a second amplifier (48) for further amplifying the output signal of the first amplifier (46); and a comparator for generating a line current monitoring signal from the output signal of the second amplifier (48). (50), wherein the output signal of the first amplifier (46) is taken out to the outside.