JPH0691557B2 - Information transmission device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a case where a plurality of terminals connected to a pair of transmission lines are AM.
The present invention relates to an information transmission device that transmits and receives information by using an I code.

[Conventional technology]

Fig. 4 shows the conventional information shown in "Investigative Research Group Report on Home Informatization (Final Report) -Technical Standardization Edition" issued by the Research Group on Informatization at Home in March 1986, for example. FIG. 5 is a circuit diagram showing a transmission device, FIG. 5 is a packet configuration diagram and a charactor configuration diagram for transmitting information, and FIG. 6 is a time showing a relationship between a signal transmitted to a transmission line and a signal transmitted from a terminal device. It is a chart. In the figure, reference numeral 1 denotes a transmission line for transmitting a signal, which is composed of a positive line 1a having a positive polarity and a negative line 1b having a negative polarity. 2,11
Is a terminal device, which is connected to the transmission path 1 and has a configuration described below. Reference numeral 3 is a transmission control device for transmitting and receiving information according to a predetermined protocol, and has an AMI code (redundancy in the amplitude direction of a signal with a packet structure and a charactor structure shown in FIGS. 5A and 5B). The transmission data plus output terminal 3a and the transmission data minus output terminal 3b are connected for transmission by the alternate mark inversion code), and output is alternately output to these output terminals 3a, 3b every time the code "0" is transmitted. put out. Reference numerals 4,5 denote transistors, the transmission data plus output terminal 3a and the transmission data minus output terminal 3b are connected to the respective base terminals to form an emitter-grounded amplifier. Reference numeral 6 is a coupling transformer, the collector terminals of the transistors 4 and 5 are connected to the primary side, and the power supply voltage is supplied to the intermediate tap 6a on the primary side. Therefore, when a current flows between the collector and the emitter according to ON / OFF of the transistors 4 and 5, an AMI-coded signal (hereinafter abbreviated as AMI signal) appears on the secondary side of the transformer 6. 7, 8 are capacitors, transformer 6
The AMI signal appearing on the secondary side of is injected into the transmission line 1 via these capacitors 7 and 8. Reference numeral 9 is an AMI decoding circuit, which is connected to the primary side of the transformer 6. The AMI signal on the transmission line 1 is input to the AMI decoding circuit 9 via the secondary side and the primary side of the transformer 6 via the capacitors 7 and 8, and the decoding result is input to the reception input terminal 3c of the transmission control device 3. To be done.

Next, the operation will be described. When the terminal 2 is connected to the transmission line 1 and a transmission request is issued to the terminal 11, for example,
After confirming that the transmission line 1 is in the idle state by the signal from the AMI decoder 9, the transmission control device 3 follows the code “k” of the start bit of each character according to the packet configuration shown in FIG. "0" is transmitted with the polarity that the plus line 1a becomes positive. That is, when the output terminal 3a is set to the high level during the start bit, the base current is supplied to the transistor 4, the transistor 4 is turned on, and the transformer 6 is turned on.
A current flows from the intermediate tap 6a to the collector of the transistor 4 on the primary side of, and a voltage is generated in the polarity of the arrow. This voltage also induces a voltage in the polarity of the arrow on the secondary side of the transformer 6, and transmits a signal having a waveform as shown in FIG. 5 (b) to the transmission line 1 via the capacitors 7 and 8. Also, when transmitting the start bit code "0", the voltage generated in the transformer 6 is also input to the AMI decoding circuit 9, the decoding result is read at the reception input terminal 3c, and the transmitted code is correctly transmitted. To confirm. Next, when transmitting the code “1”, the transistors 4 and 5 are both turned off by outputting a low level to both the output terminals 3a and 3b. That is,
Since nothing is output to the transmission line 1, the voltage becomes 0.
When the code "0" is transmitted after the code "0" of the start bit, the transistor 5 is turned on by setting the output terminal 3b to the high level, and the voltage is generated in the polarity opposite to that of the start bit. Then, the signal is output to the transmission line 1.
This enables serial transmission of the AMI code baseband signal. Also, for reception, for example, only the signal transmitted by the terminal device 11 is received by the transformer 6 via the capacitors 7 and 8, and is decoded by the AMI decoding circuit 9 as in the case of transmission, and is input to the reception input terminal 3c, The transmission control device 3 receives this.

Next, a case where the terminals 2 and 11 simultaneously start transmission will be described. 6 (a) and 6 (b) show signals that the terminals 2 and 11 are about to transmit, and FIG. 6 (c) shows signals that are actually applied to the transmission line 1. The code "0" of the start bit to be transmitted first is transmitted as the code "0" to the transmission line 1 exactly because both terminals 2 and 11 have the same polarity.
Similarly, the code "1" of the next bit does not output a signal to the transmission line 1 by both the terminals 2 and 11. Further, when the code "0" is transmitted next time, both terminals output signals in the opposite polarities to the start bit. Therefore, when both terminals transmit the same code, the transmission signal and the reception signal match and the Be transmitted to.
In the third pit, since the terminal device 2 transmits the code “0” and the terminal device 11 transmits the code “1”, the transmission line 1 is in the state where the code “0” is transmitted, and the terminal device 11 transmits the code. A mismatch between the signal and the received signal is detected and transmission is stopped. On the other hand, in the terminal device 2, since the transmission signal and the reception signal match, the transmission is continued. In this way, when a collision occurs between the terminals 2 or 11, the transmission control method "CSMA / CD win method" is realized so that one terminal wins. In order to surely perform this "CSMA / CD residual system", each of the terminals 2 and 11 needs to transmit the code "0" of the start pit to the transmission line 1 with the same polarity. If there is a terminal connected to the opposite polarity, the signal level of the transmission line 1 becomes uncertain when the start pit is transmitted, and the terminal that has collided cannot match the transmitted and received signals on both sides, and "wins". Will not be realized.

[Problems to be Solved by the Invention]

Since the conventional information transmission device is configured as described above, the polarity is confirmed when the terminals 2 and 11 are connected to the transmission line 1 so that the transmission / reception signals on the transmission line 1 do not have the same polarity. It is necessary to do so, and if there is an error in the connection of these terminal devices 2 and 11 during the installation work, there is a problem such as a cause of transmission system trouble.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain an information transmission device that can normally transmit information without checking the polarity when connecting a terminal to a transmission line. To aim.

[Means for Solving the Problems]

An information transmission apparatus according to the present invention outputs a signal for indicating a polarity to a transmission line for information transmission by a polarity setting device, and sets the polarity by a terminal device connected to the transmission line. The polarity of the transmission path is detected by the polarity detection circuit based on the signal output from the polarity setting device by serially transmitting the encoded baseband signal with a polarity having a predetermined relationship with the polarity indicated by the device. However, the polarity switching circuit switches the polarity of the baseband signal based on the output of the polarity detection circuit.

[Action]

The polarity setting device in the present invention initially sends a signal indicating the polarity to the transmission line, detects this by the polarity detection circuit provided in the terminal device, determines the polarity of the baseband signal based on this detection signal, and determines the polarity. A polarity switching signal is supplied to the switching circuit so that an encoded baseband signal having a predetermined polarity relationship with the polarity indicated by the polarity setting device is serially transmitted from the terminal device.

Example of Invention

An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, 12 is a polarity detection output terminal newly provided in the transmission control device 3, and is output when the transmission control device 3 reads the polarity of the transmission line 1. Reference numeral 13 is a transistor, which has a base terminal connected to the polarity detection output terminal 12 and drives a relay 14 connected to the collector terminal. 14a,
The contact 14b is a contact of the relay 14, the contact 14a is a make contact, and the contact 14b is a break contact. Reference numeral 15 is a polarity setting device, which shows an example of instructing the polarity by a direct current. 15
a is a power supply for supplying a direct current to the transmission line 1, 15b is a current limiting resistor connected to the power supply 15a, 15c is a switch for connecting and disconnecting the direct current indicating polarity, and 15d is a current limiting resistor 15b. Is a current detector that is connected to both ends of and detects the amount of current. Reference numeral 16 is a current limiting resistor that prevents a direct current indicating the polarity from flowing into the terminal device 2 too much, and is connected to the light emitting diodes forming the photocouplers 17 and 18 for detecting the polarity of the transmission line 1. Photo coupler 17,1
Reference numeral 8 constitutes a polarity detection circuit of the transmission line 1, and these output terminals 17a and 18a are connected to a power source through pull-up resistors 19 and 20, and the polarity detection input terminals 21 and 22 of the transmission control device 3 are connected.
It is connected to the. Reference numeral 23 is a polarity setting signal output terminal for switching the transmission polarity of the baseband signal in accordance with the signals input to the polarity detection input terminals 21 and 22, and the polarity switching circuit 24
Is connected to the control input terminal 24a. The output terminals 24b and 24c of the polarity switching circuit 24 are connected to the base terminals of the transistors 4 and 5, respectively, and the transmission data plus output terminal 3a, 3a, of the transmission control device 3 selected by the control input terminal 24a.
The output of the transmission data minus output terminal 3b is output.

Next, the operation will be described according to the flow chart of FIG. A case where the terminal device 2 is connected to the polarities shown in FIG. 1 will be described. The transmission control device 3 is initialized when the power is turned on, and then the transmission path polarity setting sequence shown in FIG. 2 is executed. The transmission control device 3 outputs a high level signal to the polarity detection output terminal 12,
Supply base current to 13. Therefore, the transistor 13
Is turned on and relay 14 is activated (step ST
1). Therefore, the contact 14a is closed and the contact 14b is opened, and the plus line 1a of the transmission line 1 → contact 14a → photo cover 17,
A loop consisting of 18 LEDs, a current limiting resistor 16 and a minus line 1b is formed. In this state, since no current is supplied from the polarity setting device 15, the outputs of the photocouplers 17 and 18 are both high level, and the transmission control device 3 reads the input level of the polarity detection input terminals 21 and 22 and there is no power supply. It is detected (step ST2). Next, when the switch 15c for instructing the polarity of the polarity setting device 15 is closed, current is supplied to the terminal device 2 via the transmission line 1. In the connection of Figure 1,
Since the current flows from the point A to the point B, the photo coupler 17 is turned on and the output becomes low level. The transmission control device 3 reads each level of the polarity detection input terminals 21 and 22, detects the start of power feeding, and then reads the polarity detection input terminals 21 and 22 a plurality of times, and the polarity of the transmission line 1 instructed by the polarity setting device 15 Read (step ST3). With this read value,
The transmission control device 3 sets the output of the polarity setting signal output terminal 23 to a high level and applies it to the control input terminal 24a of the polarity switching circuit 24. The polarity switching circuit 24 outputs the signal from the output terminal 3a.
24c operates so that the signal of the output terminal 3b is output to the output terminal 24b. That is, the polarity is set (step ST
Four). Next, the transmission control device 3 sets the polarity detection output terminal 12 to the low level and turns off the transistor 13 (step ST
5) Restore contacts 14a, 14b of relay 14. In this way, the polarity of the transmission line 1 is set. When the polarities of both terminals 2 and 11 have been set, no current flows through transmission line 1. The polarity setting device 15 detects that the current has stopped flowing by the current detector, detects the end of setting, and displays this (step ST6). When the setting end is detected, the polarity setting device 15 opens the switch 15c and disconnects it from the transmission line 1.
When a transmission request is issued to the transmission control device 3 in this state, the signal at the output terminal 3a is added to the base of the transistor 4 and the start bit is output to the plus line 1a, as in the conventional terminal device shown in FIG. . When the terminal 2 is connected with the polarity opposite to that shown in FIG. 1, the polarity is set in the same manner, and each of the terminals 2 and 11 transmits the baseband signal to the polarity instructed by the polarity setting device 15. It is possible to realize the “CSMA / CD win-win method”. Further, since the polarity detection portion unnecessary for signal transmission is cut off after the polarity is set, good information transmission can be performed without adversely affecting the signal transmission. Further, the electric power required for setting the polarity is necessary only at the time of setting and does not need to be constantly supplied from the outside.

In the above embodiment, the outputs of the photocouplers 17 and 18 are read inside the information transmission device 3 to determine the polarity of sending the baseband signal, but the polarity determining means may be provided outside the information transmission device 3. , A similar effect is obtained. FIG. 3 shows an example thereof. When the terminal 2 is powered on, the flip-flop 28 is set by the power-on reset circuit 29 connected to the reset input terminal, and the negative logic output becomes high level. Therefore, the transistor 13 is turned on, and the polarity detection circuit is formed as in the above embodiment. The outputs of the photocouplers 17 and 18 are input to the set terminal and reset terminal of the AND gate 27 and flip-flop 30, respectively. When a current is supplied to the transmission line 1 from the polarity setting device 15, either one of the outputs of the photocouplers 17 and 18 becomes low level, and the output Q of the flip-flop 30 outputs a signal corresponding to the polarity of the transmission line 1 to the polarity switching circuit. Enter in 24. On the other hand, the output of the AND gate 27 also goes low, and the delay element 31
Input to the set terminal of flip-flop 28 via. Therefore, the negative logic output of the flip-flop 28 becomes low level, the transistor 13 is turned off, the polarity detection circuit is cut off, and the polarity setting operation is completed. Masa,
The polarity setting device 15 detects that the current has stopped flowing by the current detector 15d, opens the switch 15c, and ends the operation.

〔The invention's effect〕

As described above, according to the present invention, the transmission control device specifies the polarity of the baseband signal to be transmitted to another terminal device based on the detection result of the polarity detection circuit, and the polarity switching circuit determines the polarity of the baseband signal. Since it is configured to change to the specified polarity, information can be transmitted normally without checking the polarity when connecting the transmission line and the terminal, and as a result, due to an error during installation work of the terminal. This has the effect of preventing problems in the transmission system. Further, since the polarity detection circuit is separated from the transmission line after the polarity of the baseband signal is specified, and the polarity setting device is separated from the transmission line, it is possible to prevent the information transmission / reception from being adversely affected. At the same time, there is an effect that power consumption can be reduced.

[Brief description of drawings]

1 is a circuit diagram showing an information transmitting apparatus according to an embodiment of the present invention, FIG. 2 is a flow chart showing the operation of the information transmitting apparatus according to an embodiment of the present invention, and FIG. 3 is another embodiment of the present invention. FIG. 4 is a circuit diagram showing an information transmission device according to an example, FIG. 4 is a circuit diagram showing a conventional information transmission device, and FIG. 5 is a diagram for transmitting information by the information transmission device according to an embodiment of the present invention and the conventional information transmission device. The packet configuration diagram and the charactor configuration diagram and FIG. 6 are time charts showing the signals of the respective parts of the circuit of FIG. Reference numeral 1 is a transmission line, 2 is a terminal device, 3 is a transmission control device, 15 is a polarity setting device, 17 and 18 are photocouplers, and 24 is a polarity switching circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An information transmission device in which a plurality of terminals connected to a pair of transmission lines transmit and receive information by a baseband signal, wherein the transmission line is connected to the transmission line when the polarity is instructed. A polarity setting device that outputs a signal indicating polarity to the path is provided, and the terminal device detects the polarity of the transmission path by reading the signal output from the polarity setting device, and the polarity detection circuit. While specifying the polarity of the baseband signal to be transmitted to another terminal based on the detection result of, the transmission control device that disconnects the polarity detection circuit from the transmission path after specifying the polarity of the baseband signal, and other An information transmission device, comprising: a polarity switching circuit for switching the polarity of a baseband signal transmitted to a terminal device to the polarity specified by the transmission control device.