JP2610048B2 - Terminal network controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention uses an existing telephone network and reads a measured value or the like of a meter or the like installed in a telephone user's home without ringing the bell of a telephone in the home. The present invention relates to a network controller for a terminal of an automatic data communication system in a no-ringing communication service that can be performed, and to a network controller for a terminal that controls connection between a center apparatus and a terminal device.

(Prior art)

Conventionally, for the no-ringing communication line, interface conditions are disclosed in NTT Technical Reference Material “Interface of No-ringing Communication Service”.

Here, an AC impedance of 2 kΩ or more in a no-ringing signal detection state and 600 Ω during no-ringing communication are required.

The DC impedance is 4 KΩ or more during no-ringing communication, and is as large as possible (6 KΩ or more in the case of four units) in consideration of the installation of a plurality of terminal devices during the detection of the no-ringing signal.

[Problems to be solved by the invention]

As described above, when the interface conditions are satisfied, in the process of shifting from no-ringing signal detection to no-ringing communication, both the AC impedance and the DC impedance greatly change, and impulse noise on the line, that is, a transient current increase. This leads to a reduction in current, which is not preferable.

[Means for solving the problem]

A network controller for a terminal according to the present invention is a center-side device that is connected to a terminal-side switching center via a communication line, exchanges signals with a plurality of terminal devices, and collects output data of the terminal devices; In a terminal network control device for performing data communication with the center device via a communication line and a terminal-side exchange, the DC and AC impedance of the communication line are set to predetermined values to be set during communication. , A switch for controlling the on / off of the impedance matching circuit, a photocoupler for controlling the on / off of the switch, and a connection command for connecting the terminal device and the communication circuit from the center device. Control means for connecting the impedance matching circuit to the communication circuit, and changing the DC and AC impedance of the communication line to the predetermined value. In this case, in response to the control means gradually changing the on / off duty ratio of the photocoupler, the change is equivalent to gradually changing the on / off duty ratio of the switch, and the direct current of the communication line is changed. And the AC impedance is gradually changed to the predetermined value.

[Action]

With the above configuration, the terminal network control device of the present invention, when receiving a connection command between the terminal device and the communication circuit from the center device, stops the DC and AC impedance of the communication circuit from changing smoothly, and Transient current change on the communication line does not occur, and noise due to this does not occur.

〔Example〕

Hereinafter, the present invention will be described in detail according to an embodiment of the present invention.

FIG. 1 is a block diagram of a terminal network control device for no ringing communication according to an embodiment of the present invention, FIG. 2 is a circuit diagram of an embodiment of a half-loop control unit of the present invention, and FIG. 3 (a) is a conventional timing chart, FIG. 3 (b) is a timing chart of the present invention, and FIG. 4 is a flowchart of a general control circuit of the present invention. is there.

First, if it is publicly known, it will be described according to FIG. 1. Normal line L2 is 48V, L1 is 0V, but when the polarity is reversed, L1 is 48V,
L2 becomes 0V.

Reference numeral 1 denotes a local line voltage detection unit, which detects the polarity inversion state and turns on the switcher SW12.

Then, a voltage is applied to the polarity inversion detection unit 3, a current flows through the LED of the photocoupler 4, and a signal is input to the general control circuit 5.

However, no operation is performed thereafter unless the polarity L1 and L2 no ringing signals are superimposed.

At this time, the polarity inversion detecting unit 3 is set so that the DC impedance of the local line voltage detecting unit 1 and the polarity inversion detecting unit 3 becomes high impedance within the time (350 ms) obtained under the above interface conditions. A timer circuit is provided to turn off the LED and the like of the photocoupler 4. These operations are well-known technologies, and the details thereof are omitted.

The local line voltage detector 1 monitors the local line voltage and turns on the switcher SW12 when the voltage reaches a predetermined voltage.
The polarity reversal detection unit 3 monitors the polarities L1 and L2 and the local line voltage, and turns on the photocoupler 4 when the voltage reaches a predetermined voltage.

The presence / absence detection of the no-ringing signal is detected by the amplifier 6 and the tone decoder 7 via the capacitors C1 and C2, and is input to the general control circuit 5 for determination.

The AC impedance at this time is in a high impedance state in which the above interface conditions are also required.

This is also possible with a known technique, and the details are omitted.

Next, when a no ringing signal is applied to the polarities L1 and L2, the general control circuit 5 detects the signal from the tone decoder 7, turns on the control photocoupler 8, activates the half-loop monitoring control unit 9, and activates the switcher SW2 10. Turn ON.

As a result, a DC circuit is formed with the polarity L2 → switcher SW210 → impedance matching circuit → switcher SW12 → polarity L1 to form a half loop circuit.

In the AC circuit, the polarity L2 → the capacitor C311 → the coupling transformer T112 → the polarity L1 is formed, and the impedance becomes 600Ω, and the above-mentioned interface condition is satisfied. The above is the operation of the incoming call of the no ringing communication.

This operating means is realized by the above-mentioned general control circuit 5 using a microcomputer or the like as the means described in the above interface conditions, but it is a known technique which has been variously approved, and its detailed description is omitted.

The following problem occurs when the switcher SW210 is turned on during this operation.

FIG. 2 shows a switcher SW21 comprising PNP transistors.
FIG. 3 shows a detailed diagram around 0 and a current waveform and a voltage waveform diagram of the portion, and a description will be given according to the illustrated embodiment.

Now, if the photocoupler 8 is turned on and the switcher SW210 is turned on to make the DC circuit a half loop and the AC impedance to 600Ω, the current i2 flows through the photocoupler conventionally as shown in FIG. 3 (a). .

Since this is usually performed instantaneously, the capacitor 11 shown in FIG.
, The DC resistance of this timing is small, and an overcurrent occurs in the line as shown by i0.

Also, the line voltage instantaneously drops like V1. This becomes noise and appears on the line, which is not preferable.

Therefore, according to the present invention, the current i2 of the photocoupler 8 is not instantaneously increased as shown in FIG.
Flow slowly from 10 to capacitor 11 as slow operation.

As a result, the impedance can be switched without generating noise as in the waveforms i0 and v1 of FIG. 3 (b).

The slow operation ends within the timing specified in the interface conditions as "return no ringing signal response within 3 seconds after no ringing signal detection", that is, within 3 seconds. The general control circuit 5 → tone dialer 13 → modem unit 14 → amplifier 15 → coupling transformer 12 →
What is necessary is just to make it transmit to a line via the capacitor C311.

In addition, the slow operation is performed by the switcher SW as shown in FIG.
By providing the capacitor 16 between the emitters of the PNP transistors 210, the operation can be realized even with the i2 waveform shown in FIG. 3A, but a large-capacity capacitor is required.

This slowly changes the voltage applied to VBE of the transistor around the ON voltage of VBE (approximately 0.7 V), thereby obtaining the same effect as described above. At this time, the duty flowing to i0 does not necessarily have to be linear, and the photocoupler 8 may be turned on within a period of 3 seconds as described above with a constant duty within a range where the capacitor C311 is not instantaneously charged.

This method is performed by the operation according to the flowchart of the microcomputer of the integrated control circuit 5 shown in FIG.

〔The invention's effect〕

The terminal network control device of the present invention is equivalent to the change in that the on-off duty ratio of the photocoupler is gradually changed when the DC and AC impedances of the communication circuit are blended to a predetermined value. Since the on / off duty ratio of the switch is gradually changed, and the DC and AC impedance of the communication line is gradually changed to the predetermined value, a transient current change on the communication line does not occur, and noise due to this is reduced. It can be prevented from occurring. Further, the rate of change of the DC and AC impedances to the predetermined value can be changed only by changing the on / off duty of the photocoupler without changing parts.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram of a terminal network control device for no-ringing communication according to an embodiment of the present invention, FIG. 2 is a circuit diagram of an embodiment of a half-loop control unit of the present invention, and FIG. FIG. 3 (a) is a timing chart of the related art, FIG. 3 (b) is a timing chart of the present invention, and FIG. 4 is a flowchart of the general control circuit of the present invention. FIG. 3 is a polarity reversal detector, 4 and 8 are photocouplers 5 is a general control circuit, 9 is a half-loop monitoring controller, and 10 is a switcher composed of a PNP transistor.

Claims (1)

(57) [Claims] 1. A center-side device connected to a terminal-side exchange via a communication line for transmitting and receiving signals to and from a plurality of terminal devices and collecting output data of the terminal devices; In a terminal network control device for performing data communication with the center device via an exchange, impedance matching for maintaining DC and AC impedance of the communication line at a predetermined value to be set during communication. A switch for controlling the on / off of the impedance matching circuit; a photocoupler for controlling the on / off of the switch; and a connection command for connecting the terminal device and the communication circuit from the center device when the impedance matching is performed. Control means for connecting a circuit to the communication circuit, and when changing the DC and AC impedance of the communication line to the predetermined value, In response to the control means gradually changing the on / off duty ratio of the photocoupler, the on / off duty ratio of the switch gradually changes equivalently to the change, whereby the DC and AC impedances of the communication line are changed. Is gradually changed to the predetermined value.