JPH09163017A - Network controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely obtain a desired current characteristic curve in a transistor circuit without being affected by the input signal from a telephone line by providing a changing means for changing the output signal after an amplification on the poststage of an amplifier means. SOLUTION: When the voltage of the signals inputted from the lines 15 and 16 of a telephone line is higher than the Zener voltage of a Zener diode D1, the voltage is suppressed by the Zener voltage of the Zener didoe D1. But, when the input signal is higher, the voltage is suppressed to forward direction voltage or below by the forward direction voltage of a diode D2. As for the input signal, base bias voltage is cut by a capacitor C1 and the input signal is inputted in the base of a transistor TR. When the current value of the output signal after the amplification in a transistor TR is large, the current is shunted by a resistance R5. Subsequently, the DC component is cut by a capacitor C2 in the amplified signal and the signal is supplied to the first-order side of a transducer T1. The signal is supplied to a modem, etc., from the second order side of the transducer T1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a network control device for closing a telephone line with a DC component of an input signal in a facsimile machine or the like.

[0002]

2. Description of the Related Art As a DC closed circuit in a conventional network control device of this type, a coil is used to obtain a DC component necessary for a facsimile machine or the like in order to match with a telephone line. . However, in this configuration, the coil itself is large and the circuit configuration cannot be reduced. In addition, the leakage magnetic flux from the coil may cause abnormal oscillation or a jitter phenomenon. Therefore, in order to solve these problems, it is conceivable to realize miniaturization by constructing a so-called electronic choke that artificially creates a coil component by an amplifier circuit and a passive member for making it function. Was there.

[0003]

However, there is a difference between the Japanese standard and the foreign standard in the DC characteristics of the DC closed circuit. Therefore, when manufacturing a telephone attached to a facsimile device, it was necessary to incorporate a DC closed circuit in accordance with the standards of the other country.

As shown in FIG. 4, in the DC characteristic curve 33 created by the DC closed circuit, if the current is less than a predetermined value and the voltage is more than the predetermined value in the range of the area 31, the switching equipment is excessive. An electric current flows. Further, within the range of the area 32 where the current is equal to or higher than the predetermined value and the voltage is equal to or lower than the predetermined value, the exchange facility cannot accurately monitor the circuit supplement status.

The present invention has been made in order to solve the above problems, and its purpose is not affected by the level of an input signal from a telephone line, and can be reliably achieved by a simple transistor circuit. An object of the present invention is to provide a network control device which can obtain a direct current characteristic for switching operation.

[0006]

In order to achieve the above object, in the invention described in claim 1, a changing unit for changing the output signal after amplification is provided at the stage subsequent to the amplifying unit.

According to a second aspect of the invention, in the network control device according to the first aspect, the amplifying means uses a transistor and the circuit of the transistor is formed in one stage. According to the invention described in claim 3, in the network control device according to claim 2, the base of the transistor and one of the telephone lines are connected by a diode.

Therefore, in the network control device according to the first aspect, the direct current characteristic for operating the modem etc. reliably and safely by the transistor circuit is not affected by the input signal from the telephone line. can get.

According to another aspect of the network control device of the present invention,
The one-stage transistor circuit provides the DC characteristics required for the modem according to the input signal. In the network control device according to the third aspect of the present invention, the diode can limit the forward voltage to the forward voltage or less with respect to an excessive input.

[0010]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 2, in the network control device, a ringing bell detection circuit 12 and a rectifying circuit 13 are connected to the relay switch 11 connected to the telephone lines L1 and L2, and the ringing bell is switched by switching the relay switch 11. One of the detection circuit 12 and the rectification circuit 13 is selectively connected.

The ringing bell detection circuit 12 has a telephone line L1.
The input signal from L2 is detected and the relay switch 11 is operated to switch the telephone lines L1 and L2 to the facsimile machine side or the telephone side. The rectifier circuit 13 full-wave rectifies the input signals from the telephone lines L1 and L2.

The DC closing circuit 14 is connected to the rectifying circuit 13. The primary side of the transformer T1 is connected to the DC closing circuit 20 via the capacitor C2, and the secondary side is connected to the modem via a rectifying circuit (not shown). The capacitor C2 cuts the DC component obtained by the DC closing circuit 14, and passes, for example, a tonal signal, modulation data, etc. included in the input signal.

As shown in FIG. 1, the signal rectified by the full-wave rectifier circuit DB is supplied to lines 15 and 16 of the telephone line. The Zener diode D1 has a line 15 on the cathode side and a line 16 on the cathode side after the full-wave rectification circuit DB.
The anode side is connected to the transistor T, and the rectified voltage is suppressed to a certain value or less by the Zener voltage.
Protect R.

One of the dial relays 19 is connected to the line 15 after the Zener diode D1 and the other is connected to the base of the NPN transistor TR. The dial pulse generation circuit 20 is connected to the latter stage of the Zener diode D1 on the anode side of the line 16. The dial relay 19 is turned on when the relay switch 11 is switched to the modem side, and outputs the input signals from the lines 15 and 16 to the base of the transistor TR. The dial pulse generation circuit 20 is
It is a circuit that generates dial pulses for transmission from a facsimile machine or a telephone.

The capacitor C1 and the diode D2 are connected in parallel between the rear stage of the dial pulse generating circuit 20 and the base of the transistor TR. The resistors R1 and R2 of the bias circuit are voltage dividing resistors connected between the base of the transistor TR and the line 15 and the line 18, respectively, for supplying a bias voltage to the transistor TR.

The resistors R1 and R2 and the capacitor C1 control the base voltage, and the diode D2 is to further limit the controlled base voltage. Resistance R
3 and R4 are connected between the collector of the transistor TR and the line 15 and between the emitter of the transistor TR and the line 18, respectively. Resistor R5 is line 1
5 is connected between the line 5 and the line 18 and is for shunting when the output signal of the transistor TR after amplification is large.

The capacitor C2 has lines 15 and 1
7 to cut the DC component and supply only the AC component to the transformer T1 described later. Transformer T1 1
The next side is connected to lines 17 and 18. The secondary side of the transformer T1 is connected to a modem or the like. In this embodiment, the transistor TR and the diode D2 are mainly included, the transistor TR constitutes an amplifying means, and the resistors R1 to R4 constitute a passive member.

Next, the operation of this circuit will be described by dividing it into the magnitudes of the input signals from the lines 15 and 16 of the telephone line. When the signals input from the lines 15 and 16 of the telephone line are higher than the Zener voltage of the Zener diode D1, the voltage is first suppressed by the Zener voltage of the Zener diode D1. If the input signal is still high, the forward voltage of the diode D2 is further suppressed below the forward voltage. The input signal has its base bias voltage cut by the capacitor C1 and is input to the base of the transistor TR. Also,
When the current value of the output signal after amplification in the transistor TR is large, it is shunted by the resistor R5.

The signal amplified thereafter is fed to the capacitor C2.
The DC component is cut by and is supplied to the primary side of the transformer T1. Then, it is supplied to the modem or the like from the secondary side of the transformer T1. As described above, the DC connection is performed by using the DC component to supply the AC component to the transformer T1.

When the signals input from the lines 15 and 16 of the telephone line are lower than the Zener voltage of the Zener diode D1, the base of the transistor TR is controlled by the current control by the bias circuits R1 and R2 provided before the transistor TR. The voltage is controlled and the normal transistor TR is amplified. The operation after amplification is the same as described above.

As shown in FIG. 3, if the circuit is constructed as shown in FIG. 3, in the region of the downwardly curved curve portion 23a of the direct current characteristic curve 23, the diode D2 causes the current value to change the direct current characteristic curve 23. In the region of the upwardly curved curve portion 23b in, the characteristics as shown are obtained by the Zener diode D1 and the resistor R5.

In other words, there is a conditional constraint on the region 21 when the current value is below the predetermined value and the voltage value is above the predetermined value and the region 22 when the current value is above the predetermined value and below the predetermined value. The DC characteristic curve 23 can be obtained in the region where there is no.

As described above, this embodiment has the following advantages. (1) The desired direct current characteristic curve can be reliably obtained by the transistor circuit without being affected by the input signal from the telephone line. (2) The direct-current characteristic required for the modem can be obtained according to the input signal with the one-stage transistor circuit, and the configuration is simplified and the cost is reduced. (3) The diode D2 can limit the forward voltage even to an excessive input from the telephone line to prevent the modem or the like from being damaged, and the amplification operating point is kept constant to achieve stable amplification. The operation can be secured. (4) A DC characteristic curve satisfying the standards of each country can be obtained by appropriately selecting the resistance value and the capacitance of the capacitor.

The present invention can be embodied even if it is modified as follows. (A) Change the diode D2 to a Zener diode or the like having an equivalent forward voltage drop. (B) Change from NPN type transistor to PNP type transistor, and also change other passive components such as bias resistance, emitter resistance, collector resistance, etc. (C) Shunt resistance R provided in the latter stage of the transistor TR
Change 5 to a constant current diode.

Further, the technical idea understood from the above embodiment will be described below. (1) The network control device according to claim 1, wherein a constant current diode is provided after the transistor. Even with this configuration,
A desired DC characteristic curve can be obtained. (2) The network control device according to claim 1, wherein a Zener diode is provided in a subsequent stage of the full-wave rectification circuit. According to this structure, the voltage can be suppressed to the Zener voltage or less even when the input signal from the telephone line is excessive. (3) In the DC closing circuit for closing the DC component from the telephone line, the base circuit voltage of the transistor is controlled by current control of the input signal by the bias circuit of the small signal amplifying transistor, and the output signal after amplification is If it is large, a direct-current closed circuit with a resistor for shunting the output signal after the transistor.

[0026]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, it has the following effects. According to the first aspect of the invention, the desired DC characteristic curve can be reliably obtained in the transistor circuit without being affected by the input signal from the telephone line.

According to the second aspect of the invention, the direct current characteristic required for the modem or the like can be obtained according to the input signal by the one-stage transistor circuit. According to the invention as set forth in claim 3, even if an excessive input from the telephone line is used, it is possible to limit the voltage to the forward voltage or less by the diode.

[Brief description of the drawings]

FIG. 1 is a DC closed circuit diagram in a network control device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a network control device.

FIG. 3 is a DC characteristic diagram by VI display of the embodiment.

FIG. 4 is a DC characteristic diagram based on conventional VI display.

[Explanation of symbols]

TR ... Transistor, R1 ... Bias resistance, R2 ... Bias resistance, R5 ... Shunt resistance, D2 ... Diode.

Claims (3)

[Claims] 1. A network control device comprising a closing means for closing a line and an amplifying means for amplifying an input signal inputted from the line, wherein an output after amplification is provided at a stage subsequent to said amplifying means. A network control device provided with a changing means for changing a signal. 2. The network control device according to claim 1, wherein the amplifying means uses a transistor, and the circuit of the transistor is configured in one stage. 3. The network control device according to claim 2, wherein the base of the transistor and one of the telephone lines are connected by a diode.