JPH03153156A - Signal detection circuit - Google Patents

Abstract

PURPOSE:To reduce number of components, to reduce the cost, and to make the circuit small and light in weigh by converting a current flowing to a communication line into a magnetic field, amplifying the signal in terms or DC and detecting the communication line state depending on its output change. CONSTITUTION:A detection circuit 1 consists of an electromagnetic converter 3 such as a coil interposed to a line 2 of a public line side, a Hall element 4 detecting a magnetic field (magnetic force of line) generated from the electromagnetic converter 3, a DC amplifier circuit 5 amplifying the output of the Hall element 4, an offset compensation circuit 6 compensating the offset of the DC amplifier circuit 5, a check terminal 7 from which an output of the DC amplifier circuit 5 is supplied to a control signal processing circuit and a comparator circuit 8 comparating the output of the DC amplifier circuit 5. The output of the Hall element 4 is amplified by the DC amplifier circuit 5 and the output is comparated by the comparator circuit 8.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is an NCLJ (network control unit) installed in a modem, facsimile, multi-function telephone, OA equipment, etc. connected to a wired communication line such as a public telephone line. The present invention relates to a signal detection circuit used in, etc.

(Prior art) In N CtJ etc. connected to public telephone lines etc.
The function of detecting the connection state between the public line and the exchange by detecting the DC loop current value and polarity is activated.

Figure 2 shows an NCU equipped with a conventional DC loop current detection circuit.
It is a circuit diagram showing an example of -.

A DC loop current detection circuit 101 shown in this figure is an electromagnetic converter 1 such as a coil inserted into a line 102 on the public line side.
03, a Hall element +04 that detects the magnetic field generated by this electromagnetic transducer 103, and an amplifier 105 that amplifies the output of this Hall element 104.
When the voltage applied to 02 is reversed and the direction of the current flowing through the coil changes, this is detected and supplied to the modem body, etc.

By the way, in public communication lines, N is generally used to compensate for the withstand voltage between the four communication wires and the modem's main circuit
In CtJ, the line transformer 106 transmits audio signals etc. supplied from the public line side to the modem side, etc.
Also, high transformer (high impedance transformer) +07
extracts control signals such as ringer signals and facsimile signals supplied from the public line, and sends them to amplifier +08, bandpass filter 109,
Control signal detection circuit I configured by amplifier 110 etc.
Since detection is performed using l+, there is a problem in that the number of parts is large, making it difficult to reduce costs, make the circuit smaller, and make it lighter.

(Objective of the Invention) The present invention was made in order to solve the conventional problems as described in 1.1. The purpose of this invention is to provide a signal detection circuit that can detect signals.

(Summary of the Invention) In order to solve the above problems, the detection circuit according to the present invention includes an electromagnetic transducer that converts the current flowing through the 11-circuit line into a magnetic field, and a magnetic field obtained by the electromagnetic converter. A magneto-electric converter for converting into an electric signal, a DC amplifier circuit for DC amplifying the output of the magneto-electric converter, a comparator circuit for detecting the state of the three circuits based on changes in the output of the DC amplifier circuit, and the DC amplifier. It is characterized by having a terminal for leading the output of the circuit to the outside.

(Embodiments) The present invention will now be described in detail based on illustrated embodiments.

FIG. 1 is a block diagram showing one embodiment of the present invention.

The main circuits of the N CtJ shown in this figure are a detection circuit 1 that detects reverse signals, Kanade 1.1, facsimile Iha, etc. supplied from the public line side, and 5 public 1 [supplied from the 1 line side. It is equipped with a line transformer 20 that transmits audio signals etc. to the modem side etc.

The detection circuit 1 includes an electromagnetic transducer 3 such as a coil inserted into the line 2 on the public line side, a Hall element r-4 that detects the magnetic field (magnetic field lines) generated by the electromagnetic transducer 3, and a Hall element r-4 of the Hall element 4. A DC amplifier circuit 5 that amplifies the output, an offset compensation circuit 6 that compensates for the offset of the DC amplifier circuit 5, and a check terminal 7 that supplies the output of the DC amplifier circuit 5 to a control signal processing circuit (not shown). and 11
A comparator circuit 8 that compares the output of the DC amplifier circuit 5 is provided.

+iii. The DC amplifier circuit 5 includes an inverting input type Kawaguchi amplifier 9, a resistor lO serving as a feedback resistance of the operational amplifier 9, and a resistor ll serving as a human resistance of the operational amplifier 9,
The output of the 675 Hall element T4 is DC amplified and supplied to the comparator circuit 6, and is controlled via the IFI check terminal T-7 and a capacitor (not shown) connected to the check terminal r. A. Supplied to No. 11 processing circuit.

The comparator circuit 8 is 1F obtained by dividing the reference voltage.
Comparing the side reference voltage Vrer with the output of the 11 current amplifier circuit 5, +E side reference voltage IF, 11; from Vref.
1. When the output of the DC amplifier circuit is large (when the public line is not reversed), the comparator 12 generates a signal and outputs it from the output terminal 21, and the t1 side reference voltage obtained by dividing the base voltage. −■ rcf and the output of the DC amplifier circuit 5 described in 11 are compared to determine the negative side reference voltage −V r
and a comparator 13 that generates a "1" signal and outputs it from the output terminal 22 when the output of the DC amplifier circuit 5 is smaller than er (when the public line is in reverse), and the public line is not in the reverse state. Sometimes, the comparator 12 detects this and outputs a "1" signal, and when the public line is in the reverse state, the comparator 13 detects this and outputs a "1" signal.

Further, the offset compensation circuit 6 includes a resistor 14 and a variable resistor 16 that divide the reference voltage, an amplifier 17 that amplifies the voltage obtained by these resistors 15 and the variable resistor 16, and an output of the amplifier 17 that is connected to the DC amplifier circuit 5. 6) generates an offset voltage according to the value set in the variable resistor 16, inputs it to the DC amplifier circuit 5, and outputs the offset voltage of the DC amplifier circuit 5. Adjust.

As described above, in this embodiment, the output of the Hall element 4 is amplified by the DC amplifier circuit 5, and this output is compared by the comparator circuit 8, so that when the public line side is in the reverse state, this can be detected. In history, check the output of the DC amplifier circuit 5 at terminal r7. Since the signal is supplied to the control signal processing circuit via a capacitor, the signal obtained by pulsing the 1r+ current is supplied to the control signal processing circuit and the call No. 1.1 and facsimile included in this signal are processed. (, E, etc. can be extracted.

This allows high transformers and control 1. It is possible to omit the + sign detection circuit, etc., and as a result, the number of parts is reduced compared to conventional circuits, reducing costs and making the circuit smaller and lighter;
1 can be achieved.

In addition, in the history, the terminal r7 that leads the DC amplifier circuit output to the outside has not only control (+T';) but also 77,
, j and i are also transmitted, so f is transmitted from the terminal r7 to the modem without going through the high transformer 20 shown in FIG.
, it is also possible to convey the number.

However, in order to send the f'ri signal from the modem to the ri line side, a high transformer 20 is required.

If this is changed to other means, the high transformer 20 will become unnecessary.

(Effects of the Invention) As described above, according to the present invention, the number of components can be reduced to achieve cost reduction, miniaturization of the circuit, and reduction in load.

[Brief explanation of the drawing]

FIG. 1 shows an N
Figure 2 is a circuit diagram showing the part of the CIJ.
FIG. 2 is a circuit diagram showing the main parts of C[1. 1...Detection circuit, 2...Public four-track line, 3.
...Electromagnetic converter, 4...Magnetoelectric converter (Hall Furyo),
5... DC amplifier circuit, 7... Output circuit (check terminal r), 8... Comparator circuit.

Claims (1)

[Claims] (1) An electromagnetic converter that converts the current flowing through the communication line into a magnetic field, a magnetoelectric converter that converts the magnetic field obtained by the electromagnetic converter into an electric signal, and a DC amplify the output of the magnetoelectric converter. A signal detection circuit comprising an amplifier circuit, a comparator circuit that detects the communication line state based on a change in the output of the DC amplifier circuit, and a terminal that outputs the output of the DC amplifier circuit to the outside.