JPH0270165A - Terminal equipment for network controller - Google Patents

Abstract

PURPOSE:To prevent an operation at the time of voltage below the prescribed voltage by providing a transistor in which a Zener diode is connected to an emitter, and providing the base of this transistor with a variable resistor to adjust a base current. CONSTITUTION:When a C-NCU 6 for gas calls out s terminal equipment 3 for gas, the NRT 9 of a telephone line network 2 calls out the line of a telephone set 1, and performs the decision of the sum of the current values of respective terminal equipments 3 to 5 connected to the telephone set 1. If it is below 20mA, it inverts the polarity of the voltage to be impressed upon the respective terminal equipments 3 to 5. Consecutively, it sends a selection signal to call out the terminal equipment 3 for gas from the C-NCU 6 for gas. As the result, the terminal equipments 4,5 are connected to the signal line of the telephone line network 2 through a resistor over 2 MOMEGA, and as for the terminal equipment 3 for gas with which the selection signal coincides, the phototransistor 33 of a current control circuit 13 is turned on, and the resistor 34 is by-passed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a terminal device that is called by a network control device using a no-ringing trunk of a telephone line network.

[Conventional technology]

Network control devices (telemeters, telecontrol system) is known.

This network control failure, telephone port number & network control device connected to the network, no-ringing trunk installed in the telephone line network,
It consists of a terminal device that can communicate with a network control device via a telephone line network, and the network control device calls the terminal device via a no-ringing trunk of the telephone line network, and transmits the data obtained by the terminal device to the telephone line network. It is transmitted to the network control device via the network controller.

[Problems to be Solved by the Invention] A no-ringing trunk calls a terminal device, bypasses a resistor of the terminal device whose resistance value is greater than or equal to a predetermined resistance value (INΩ or more), and connects the terminal device to enable communication with a telephone line network. The polarity of the voltage applied to the device is reversed.At this time, the terminal device detects that the reversed voltage is higher than a predetermined voltage (36V or higher).
) The terminal equipment is not allowed to operate until the voltage is increased to ).

Furthermore, when the terminal device is in a loop state (more than 20 mA flows through the terminal device), the no-ringing trunk determines that the telephone connected to the terminal device is in use and cuts off communication.

This means that when multiple terminal devices are connected to one telephone, the total current value of each terminal device is within the half-loop range (
(less than 20m8).

Then, the no-ringing trunk selects and inverts the polarity, and the inverted voltage is set to a predetermined 1°C pressure voltage (36V
The terminal device whose voltage has been increased to (above) is connected to the telephone line network by bypassing the resistor having a predetermined resistance value. This causes a problem in that the voltage applied to the terminal device drops, and the voltage applied to the terminal device drops below a predetermined voltage (36V).

Furthermore, due to variations in equipment, there was a possibility that the terminal device would operate even though the predetermined voltage (36V) was not reached.

The present invention has been made in view of the above circumstances, and even if the voltage applied from the telephone line network to the terminal device increases to a predetermined voltage or higher and then drops below the predetermined voltage, the telephone line network and the terminal device do not The purpose of this is to maintain the connection between devices, and to prevent the terminal device from operating below a predetermined voltage due to device variations.

[,7! Means for Solving the Problem] In order to achieve the above object, the present invention is configured to connect to a signal path of a telephone line network via a resistor having a predetermined resistance value or more, and to transmit a voltage of a predetermined voltage or more from the telephone line network. bypassing the resistor in the signal path to enable communication with the telephone network; after bypassing the resistor;
Technical means include a hold circuit that bypasses the resistor in the signal path and maintains a state in which communication with the telephone network is possible even if the voltage applied from the telephone network drops below the predetermined voltage. shall be.

In addition, as a means for bypassing the resistor by applying a voltage of [predetermined voltage device]-, a transistor with a Zener diode connected to the emitter is provided, and a variable resistor for adjusting the base current is provided at the base of this transistor. .

Functions and Effects of the Invention] The present invention having the above-mentioned configuration is capable of controlling the polarity of the voltage applied to the terminal device by the no-ringing trunk interposed in the telephone line network when the network control device calls the terminal device via the telephone line network. A reversal occurs.

After the polarity is reversed, when the voltage applied to the terminal device exceeds a predetermined voltage, the resistor having a predetermined resistance value or more is bypassed, and the terminal device and the telephone network are connected for communication. Then,
The voltage applied to the terminal device decreases, but due to the function of the hold circuit, even if the voltage applied to the terminal device decreases, the resistor with a predetermined resistance value or more is bypassed, allowing communication between the terminal device and the telephone line network. maintained in good condition.

In addition, by adjusting the variable resistor, the current value applied to the base changes, and by changing the voltage between the base and emitter of the transistor, variations in the Zener diode can be adjusted, and the terminal device can be It can be easily prevented from operating.

[Embodiment] Next, a terminal device of a network control device according to the present invention will be described based on an embodiment shown in the drawings.

FIG. 2 shows a schematic block diagram of a telemetry system using the present invention.

Telephone 1 is connected to other telephones via telephone line 12I2. The telephone 1 shown in this embodiment includes:
A gas terminal device 3 for detecting the amount of gas used in the household where the telephone 1 is installed, an electricity terminal device σ4 for detecting the amount of electricity used, and a water terminal device 5 for detecting the amount of tap water used are connected. ing.

In addition, the gas supply company has a gas center network control unit (hereinafter referred to as gas C-NCU) 6 that detects the amount of gas used by each household via the telephone line network 2, and the electric power company has a A network control device for an electricity center (hereinafter referred to as an electricity C-NCU) that detects household electricity usage via the telephone line 112.
)7-Waterworks stations are each provided with a waterworks center network control device (hereinafter referred to as waterworks C-NCU) 8 that detects the amount of tap water used by each household via the telephone line network 2.

The telephone line w: I2 has a no-ringing trunk that prevents the doorbell of the telephone 1 connected to each terminal device 3 to 5 from ringing when each C-NCU 6 to 8 calls each terminal device 3 to 5. (hereinafter referred to as NRT) 9 is interposed.

This NRT9 requires that when one of the C-NCts 16 to 8 calls one of the terminal devices 3 to 5, the total current value of the terminal devices 3 to 5 to be called must be less than 20 mA (half loop state). When the half-loop condition is satisfied, the NRT 9 reverses the polarity of the voltage applied to each terminal device 3 to 5. Each of the terminal devices 3 to 5 is stipulated not to operate until the applied voltage reaches 36 V (predetermined voltage) or higher after the polarity is reversed. Furthermore, if the sum of the current values applied to each of the terminal devices 3 to 5 during communication exceeds 20m8 (loop state), the NRT 9 will cut off the telephone line, assuming that the connected telephone 1 is being used.

Further, each of the terminal devices 3 to 5 has a telephone line l12I.
When not communicating with each C-NC06-8 via 2,
A resistor with a predetermined resistance value of 1 HΩ or more (10) in FIG. 1 is interposed between the telephone line IIq2 and the telephone line network 2, so that each C - When communicating with the NCs 06 to 8, communication is enabled by bypassing the intervening resistor 10.

Therefore, as shown in FIG. 1, the signal input section of each terminal device 3 to 5 includes a hold circuit 11, a reset circuit 12,
ri! consisting of the current side m circuit 13! An l-line switching circuit 14 is provided respectively.

The hold circuit 11 includes two transistors 15, 16 .
5 resistors 17-21. 1 Zener diode 2
2. Consists of one variable resistor 23. and,
In this embodiment, when 36V or more is applied to the line switching circuit 14, the voltage division ratio of the resistor 17.19 causes the transistor 1 to
5 is set to be turned on. Also transistor 1
Reference numeral 6 is for self-holding of the transistor 15, and when the transistor 16 is turned on, the transistor 15 is turned on until the reset circuit 12 is activated even if the base voltage applied to the transistor 15 drops. The Zener diode 22 prevents the transistor 15 from turning on when a voltage of less than 36 V is applied to the line switching circuit 14, and the variable resistor 23 adjusts the current value applied to the base of the transistor 15. By adjusting the voltage between the base and emitter of the transistor 15, variations in the Zener diode 22 can be adjusted, and the resistor 10 can be prevented from being bypassed when a voltage of less than 36V is applied due to variations in the Zener diode 22. be.

Further, the reset circuit 12 includes two phototransistors 24, 25, two transistors 26, 21, three resistors 28 to 30, and two capacitors 31, 32.

Further, the current control circuit 13 includes one phototransistor 33 and a resistor 34.

Note that the phototransistors 24, 25, and 33 are light emitters (for example, photodiodes) whose energization is controlled by a computer (not shown) installed in each terminal device 3 to 5.
It is controlled by ON and F.

Reference numeral 35 shown in the figure represents a diode, and reference numeral 36 represents a primary coil of an impedance matching transformer.

Next, the operation of the line switching circuit 14 will be explained based on, for example, a case where a gas supply company performs automatic meter reading.

When the gas C-NCU 6 calls the gas terminal device 3,
The NRT 9 of the telephone line network 2 calls the line of the telephone 1 and determines whether the phase of the current value of each terminal device 3 to 5 connected to the telephone 1 is less than 20mA, and if it is less than 20mA, The polarity of the voltage applied to each terminal device 3 to 5 is reversed. Then, the voltage of -48v applied to each terminal device 3 to 5 changes to 148v.

When 36V is applied to the bold circuit 11 of each terminal device 3 to 5, the transistor 15 turns ONL, then the transistor 16 turns ONL, bypassing the resistor 10 of 1 HΩ or more, and each terminal device 3 to 5 connects to the telephone line. It is communicably connected to the gas C-NC 116 via 1'l12. At this time,
The phototransistor 33 of each current control circuit 13 is OFF
A resistor 34 is arranged in the signal path, and each terminal device 3
The sum of the current values of 5 to 5 is less than 20 mA.

Subsequently, a selection signal for calling the gas terminal device 3 is transmitted from the gas C-MC 116.

Then, the selection signals of the gas terminal device 3 match, and the selection signals of the electricity terminal device 4 and the water terminal device 5 do not match. For this reason, the phototransistor 2 of the reset circuit 12 is activated by the computer in the main body of the terminal device 4.5.
4.25 is turned ON for a short time, transistors 15 and 16 of the hold circuit 11 of the terminal device 4.5 are turned OFF, and the reset circuit 12 turns the transistor 15 to 0IIL.
It is self-maintained so that it does not occur. As a result, the terminal device 4.5
is a telephone line via a resistor 10 of 1 HΩ or more! I2I2
connected to the signal path of

On the other hand, the gas terminal device 3 with the matching selection signal consumes power for transmission etc., so within a range of less than 20m8,
In order to obtain as much current as possible, the phototransistor 33 of the current control circuit 13 is turned on, and the resistor 3
4 is bypassed.

Thereafter, in accordance with the format of automatic gas meter reading, the gas terminal device 3 transmits the amount of gas used in the home where the telephone 1 is installed to the gas C-NCU 6 of the gas supply company.

When the transmission of the gas usage amount is completed, the current control circuit 13 is activated by the computer in the main body of the gas terminal device 3.
At the same time, the phototransistor 33 of the reset circuit 12 is turned ON for a short time, and the transistor 15.16 of the hold circuit 11 of the terminal device 4.5 is turned ON.

As a result, the gas terminal device 3 has a resistor 10 of 1 HΩ or more.
It is connected to the telephone line network 2 via.

According to this embodiment, after the gas C-NCU 6 and the gas terminal device 3 are connected by bypassing the resistor 10, even if the voltage applied to the gas terminal device 3 decreases to less than 36V,
By the function of the hold circuit 11, the connection state is maintained so that the gas C-NCU 6 and the gas terminal device 3 can communicate with each other.

(Modified Example) In this embodiment, an example in which the present invention is used in a telemeter system is shown, but it may also be used in a telecontrol system.

Although an example has been shown in which the hold circuit is constructed using two transistors as a self-holding circuit, the self-holding circuit may be constructed using other circuits such as a flip-flop circuit.

[Brief explanation of the drawing]

FIG. 1 is an electrical circuit diagram of a line switching circuit including a hold circuit, and FIG. 2 is a schematic block diagram of a telemeter system.

Claims (1)

[Scope of Claims] 1) Connected to a signal path of a telephone line network via a resistor having a predetermined resistance value or more, and applying a voltage of a predetermined voltage or more from the telephone line network to the resistor in the signal path. to enable communication with the telephone line network, and after bypassing the resistor, bypass the resistor in the signal path even if the voltage applied from the telephone line drops below the predetermined voltage. A terminal device of a network control device, comprising a hold circuit that maintains a state capable of communicating with the telephone line network. 2) A claim comprising a transistor whose emitter is connected to a Zener diode as a means for bypassing a resistor by applying a voltage higher than a predetermined voltage, and a variable resistor is provided at the base of this transistor to adjust the base current. Terminal device of the network control device according to item 1.