JPH03293853A - Terminal network controller - Google Patents

Abstract

PURPOSE:To prevent the occurrence of noise on a line at the time of switching connection to satisfactorily communicate data by providing a specific switch means which connects a telephone line to a half loop impedance matching circuit by switching at the time of switching to no-ninging communication. CONSTITUTION:A photocoupler 2 is used as a half loop control circuit 3 and is interposed between telephone lines L1 and L2 and a half loop impedance matching circuit 14 as the half loop circuit. After a pulse alternating driving signal whose on/off duty ratio is gradually increased is outputted to a light emitting element 2a of the photocoupler 2 for a prescribed time at the time of reception of a no-ringing signal from a CPU circuit 1 as the control circuit, a turning-on driving signal is outputted to gradually making a light receiving element 2b as the switch of the telephone line L1 conductive. Thus, a transient current due to quick connection or the like does not flow to telephone lines L1 and L2, and the line voltage is not transiently reduced, and data commundation is not hindered by noise.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a terminal of an automatic data communication system that performs data communication between a sensor device such as a meter reading meter of the terminal and a central device using a no-ringing communication line. It relates to a network control device.

<Prior Art> Conventionally, as this type of terminal network control device, one shown in FIG. 5, for example, is known. This terminal network control device controls subscriber telephone lines Ll and L2 at the start of no-ringing communication.
a polarity reversal detection circuit II that detects the polarity reversal of the detection circuit II; a photocoupler 18 that triggers the CPU circuit 21 based on the detection signal of the detection circuit 11; and a control signal that is input from the CPU circuit 21 via the photocoupler 19 in response to the trigger. When a no-ringing call is received, subscriber telephone line L1.
NR9 detection control circuit I2 that connects L2 to one coil of line coupling fl15 and maintains the coil side at high impedance (for example, AC impedance 2 is Ω, DC resistance value 16 is Ω) for a predetermined time (for example, 350 m5ec);
It has an NR5 detection circuit 16 that detects a no-ringing signal (hereinafter abbreviated as NRS) induced in the other coil of the line coupling section 5.

Furthermore, when the terminal network control device determines that the NRS detected by the NR8 detection circuit 16 is for its own terminal, the terminal network control device
In response to a control signal input from the U circuit 21 via the photocoupler 20, the subscriber telephone line L is connected during no-ringing communication.
Impedance matching circuit 1 when moving l and L2 by half a step
a half-loop control circuit 13 that connects to 4 and maintains the circuit impedance at an appropriate value (for example, AC impedance 600Ω, DC resistance 4Ω); and an interface circuit 22 that outputs data such as a meter reading meter to the CPU circuit 21. and a modem circuit 17 that is connected to the other coil of the line coupling section 15 and the CPU circuit 21 and modulates and demodulates data for transmission and reception.

Therefore, the polarity reversal detection circuit 11 detects the polarity reversal of subscriber telephone lines Ll and L2 at the start of no-ringing communication,
By the trigger of the detection signal passing through the photocoupler 18, the CPU
The circuit 21 outputs a control signal via the photocoupler 19,
Using this control signal, the NR8 detection control circuit 12 connects the subscriber telephone lines Ll and L2 to the high-impedance line coupling section 15 side for a predetermined period of time, and transmits the NR9 input via the other coil and the NRS detection circuit 16 to the CPU circuit. 2I will monitor. Then, when the NRS input within the predetermined time is for the own terminal, the CPU circuit 21 outputs a control signal to the half-loop control circuit 13 via the photocoupler 20, and Turn on the relay contacts that are not connected as shown in FIG. 6(c), and connect the subscriber telephone lines Ll and L2.
is connected to the half-step impedance matching circuit 14 side of the appropriate impedance. As a result, the terminal network control device shifts from the NR5 detection state to no-ringing communication.

<Problems to be Solved by the Invention> However, in the conventional terminal network control device, when NR5 for the own terminal is input, the relay contact in the half-loop control circuit 13 is instantaneously turned off as shown in FIG. 6(c). Since it is turned on to connect subscriber telephone lines Ll and L2 to the half-step impedance matching circuit 14 side, the capacitor 23 shown in FIG. 5 is charged at the moment it is turned on, and the subscriber telephone lines Ll
, L2 as shown in FIG. 6(b), and the line voltage v1 also momentarily drops as shown in FIG. 6(a).
, noise occurs on L2 and interferes with data communication)
There are some drawbacks.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to prevent the generation of noise on the line at the time of switching connection by devising a switch means and its control for switchingly connecting the telephone line to the half-step impedance matching circuit when transitioning to no-ringing communication. An object of the present invention is to provide a terminal network control device that can perform good data communication.

Means for Solving the Problems> In order to achieve the above object, the present invention utilizes a no-ringing trunk provided at the terminal-side switching center to connect the sensor device and the central device without ringing the telephone of the terminal. In a terminal network control device for an automatic data communication system that performs data communication, there is a half-loop circuit that has a predetermined AC impedance and DC resistance value and is connected to a telephone line to form a half-loop during data communication, and an on/off circuit. A photocoupler consisting of a light-receiving element and a light-emitting element is provided to connect and disconnect the telephone line and the half-loop circuit, and the light-emitting element of the photocoupler receives a no-ringing signal to turn on and off.
The present invention is characterized in that it includes a control circuit that outputs an on-drive signal after outputting a pulse-like alternating drive signal in which the off-duty ratio gradually increases for a predetermined period of time.

Function> Now, suppose that NR5 (no-ringing signal) is input to the terminal network control device via the telephone line using the no-ringing trunk of the terminal-side exchange.

Then, upon receiving this NRS, the control circuit sends a pulsed alternating drive signal with a gradually increasing on/off duty ratio to the photocoupler light emitting element interposed between the telephone line and the half-loop circuit at a predetermined time. After all outputs are completed, an ON drive signal is output. The light-emitting element of the photocoupler emits light intermittently in short cycles according to the duty ratio, and the light-receiving element that receives this light begins to conduct when the duty ratio exceeds a certain value, and becomes completely conductive when the duty ratio reaches a certain larger value. conducts to. As a result, the telephone line is gradually connected in a half-loop circuit, so transient currents do not flow through the telephone line as would be the case with rapid connections, the line voltage does not drop transiently, and data communication is inhibited by noise. You will no longer be exposed to it.

<Example> Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 1 shows an example of the main parts of a terminal control device of the present invention. The main parts shown in FIG. 1 correspond to the half-loop control circuit 13, photocoupler 20, and CPU circuit 21 of the terminal network control device described in FIG. 5, and other than the above-mentioned main parts of the terminal control circuit of the present invention. The configuration is the same as that shown in FIG.

As shown in FIG. 1, the main parts mentioned above are constructed using the same photocoupler 20 (see FIG. 5), omitting the conventional photocoupler 20 (see FIG. 5).
as a new half-loop control circuit 3 for telephone lines Ll and L2.
and the half-step impedance matching circuit 14 which is a half-loop circuit. After outputting a pulsed alternating drive signal in which the value gradually increases over a predetermined period of time, an ON drive signal is outputted to gradually bring the light receiving element 2b, which is a switch of the telephone line L1, into conduction. Note that the pulsed alternating drive signal and the on-drive signal are provided in FIG. 1 by applying a power supply voltage to the light emitting element 2a via a resistor 4 and a switch 5, and turning the switch 5 on and off by a CPU circuit l. This can actually be realized by simply connecting the light emitting element 2b to the I10 port of the CPU circuit 1.

Figure 2 shows the current signal ■ which is the above-mentioned pulsed alternating drive signal.
2 is a timing chart showing waveforms of . When the CPU circuit 1 receives an NRS (noring signal) for an automatic terminal, the CPU circuit 1 turns on time T as shown in FIG. While keeping constant, the off time Ti (i = 1 to n) is gradually shortened,
3. Generate n patterns whose duty ratio gradually increases, and output each pattern to the light emitting element 2a by 2/n seconds in order from the pattern with the shortest average on time per unit time Tu.
(See figure (c)), and from 2 seconds onwards, an ON drive signal of "H" (duty ratio 100%) is output at all times. In addition, above-
Fixed on time T. is determined by the minimum instruction time of the CPU circuit 1 and the electro-optical transfer characteristics of the photocoupler 2.

A pulsed alternating drive signal l whose duty ratio gradually increases.
Since the photocoupler 2 that receives , has variations in electrical and optical transfer characteristics, the light receiving element 2a starts to conduct at, for example, the j-th pattern among the n patterns shown in FIG. 3(c), and gradually becomes conductive. By increasing the proportion of , the second pattern becomes completely conductive. Therefore, the current 11 flowing from the telephone line Ll to the impedance matching circuit 14 during half-step is as follows:
As shown in Figure 3 (b), there is a transient change (Figure 6 (b)
), and the line voltage V1 also increases to the third level.
As shown in Figure (a), the noise gradually decreases and no noise occurs on the telephone lines L1 and L2. In other words, the telephone line L1. By switching L2 from the high-impedance line coupling section 15 (see Figure 1) side to the proper impedance half-step impedance matching circuit 14 side, it is possible to transition from the NRS reception state to the no-ringing communication state. .

The operation of the main parts of the terminal network control device having the above configuration (see FIG. 1) will now be described with reference to the flowchart of FIG. 4.

Now, the photocoupler 2 of the half-loop control circuit 3 is non-conducting,
The NRS detection control circuit 12 (see FIG. 5)
1 and L2 are connected to the high-impedance line coupling section 15 side, the line coupling section 15. Through the NR3 detection circuit 16, the CPU circuit 1 connects the telephone line L1. Assume that NRS on L2 is received. Then, the CPU circuit 1 becomes
In steps S1 and S1'', the current signal 2, which is an alternating drive signal of the first pattern (on time T0, off time T,) with the minimum duty ratio, is output to the light emitting element 2a of the photocoupler 2 for 2/n seconds.Next, , In step S2.S2', a second pattern (on time To, off time T) with a slightly increased duty ratio is output in the same manner as the current signal I, G2/n seconds, and after 2 seconds while the duty ratio is further increased slightly. The output operation is repeated until the current signal I of the nth pattern in steps Sn and Sn' is output, and in step S(n+1), an ON drive signal of "H" is output at all times.During this time, the light emission is performed as the duty ratio gradually increases. The amount of light emitted by the element 2a increases, and the light receiving element 2b that receives this starts to conduct in the nth pattern, gradually increases the rate of conduction, and becomes completely conductive in the second pattern.Therefore, as described above, noise It is possible to switch the telephone lines Ll and L2 from the line coupling unit 15 side to the half-step impedance matching circuit 14 side without causing any noise, and to transition from the NR9 reception state to the no-ringing communication state, and the rapid communication using conventional relay contacts is possible. This eliminates interference with data communications due to noise, which was a disadvantage of conventional switching.

It goes without saying that the present invention is not limited to the illustrated embodiment.

<Effects of the Invention> As is clear from the above explanation, the terminal network control device of the present invention provides a photocoupler between a half-loop circuit having a predetermined AC impedance and DC resistance value and a telephone line to connect the two. At the same time, the control circuit that receives the no-ringing signal outputs a pulse-like alternating drive signal whose on/off duty ratio gradually increases to the light-emitting element of the photocoupler for a predetermined period of time, and then outputs an on-drive signal. Because of this, the connection to the telephone line can be gradually switched from the circuit for NRS reception to the half-loop circuit for no-ringing communication, preventing noise caused by transient currents occurring in the telephone line.
Good data communication can be performed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the main part of the terminal control device of the present invention, FIG. 2 is a timing chart showing a pulsed alternating drive signal supplied to the photocoupler of FIG. 1,
Figure 3 shows the above alternating drive signal. Figure 4 is a flowchart showing the control procedure of the CPU circuit in Figure 1, Figure 5 is a block diagram of a general terminal network control device, and Figure 6 is a diagram showing changes in line voltage and single line current. FIG. 3 is a diagram showing changes in line current, etc. 1...CPU circuit, 2...Photocoupler, 2a...
Light emitting element, 2b... Light receiving element, 3... Half loop control circuit, 14... Half step impedance matching circuit, Ll, L2... Telephone line, 11... Line current, Vl
...Line voltage, 1. ...Pulsed alternating drive signal.

Claims (1)

[Claims] (1) In a terminal network control device of an automatic data communication system that uses a no-ringing trunk installed at a terminal-side switching center to perform data communication between a sensor device and a central device without ringing the terminal telephone, A half-loop circuit that is connected to a telephone line to form a half-loop during data communication, and a half-loop circuit that has an AC impedance and a DC resistance of After receiving a no-ringing signal and outputting a pulsed alternating drive signal with a gradually increasing duty ratio of on/off to the photocoupler consisting of a light-receiving element and a light-emitting element, the light-emitting element of the photocoupler is turned on. A terminal network control device comprising a control circuit that outputs a drive signal.