JPS5922427B2 - Signal transmission method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal transmission system in which a large number of communication devices mutually transmit signals via a common line using an optical coupling element.

2. Description of the Related Art Conventionally, a method called a closed loop method is known as a transmission/reception method between various terminal devices such as data communication or between a control device and a terminal device.

An example of such a conventional method is Japanese Patent Application No. 48-2363.
No. 5, and Japanese Patent Application No. 49-47814. In such conventional systems, a plurality of communication devices use l pairs of transmission lines for transmission in both directions, sending and receiving, and when data transmission is not being performed, the transmission line is powered by a power supply for the line. υ
A current is constantly flowing through the device, and when data is being transmitted, this current is intermittent to send the data to other communication devices.
In this method, the transmission line and equipment are separated by direct current, so there is no effect of earth potential difference between the transmitting and receiving points, and transmission and reception can be performed between communication devices. However, the required voltage of the line power supply is connected in series with the line. Depends on number of devices. In addition, when a communication device is removed from this transmission line, the transmission line becomes an open loop, and communication between other communication devices becomes impossible.
Furthermore, it has the disadvantage that current must always be kept flowing through the transmission line even when data is not being transmitted. The present invention has been made to take advantage of the desirable features of the conventional method and eliminate its drawbacks, and is the same as the conventional method in that it uses optical coupling elements to provide direct current isolation between each device and the transmission line. Even if the transmission line of multiple devices is damaged or removed, there is no problem with transmission and reception between other devices, and the power supply for the transmission line is independent of the number of communication devices connected to the transmission line. It can be determined by

Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 1 shows an embodiment of the transmission/reception system according to the present invention, with T1 to
Tn is a communication unit, 1 is a transmission line made of, for example, two twisted wires, 2 is a connector terminal, and communication units T1 to T
n are mutually connected in parallel to the transmission line 1 via the connector 2. Each of the communication units T1 to Tn is configured to have a connecting section 3 for connection to a line and a transmitting/receiving section 4 for transmitting and receiving signals to and from other communication units.

The connecting section 3 and the transmitting/receiving section 4 of each communication unit are coupled using an optical coupling element, that is, a transmitting optical coupling element and a receiving optical coupling element, as is well known. The light-emitting element emits light due to the current of the light-emitting element, and the light-receiving element receives this light to change the current of the light-receiving element.

In the figure, a photocoupler 51 is shown as a transmitting optical coupling element, and a photocoupler 52 is shown as a receiving optical coupling element. Next, the configurations of the transmitting/receiving section 4 and the connecting section 3 will be explained using the communication device T1 as a representative. The light emitting element 41 of the transmitting optical coupling element 51 is driven so that the current flowing therein changes according to a transmitting signal from a transmitting output circuit (not shown).

On the other hand, the light receiving element 42 of the receiving optical coupling element 52 is adapted to receive light from a light emitting element 32, which will be described later, and to send a received signal to a receiving circuit (not shown). Next, the configuration of the connecting portion 3 will be described. The light emitting element 32 is connected in series with the power source V and the resistor R1, and is connected to the transmission line 1 via the connector 2. On the other hand, one end of the light receiving element 31 is connected to one end of the power supply V via a resistor R2 to apply an operating voltage, and the other end of the light receiving element 31 is coupled to the human power side of the switching element Q. The switching element Q is similarly connected to the transmission line 1 via the connector 2.
The other communication units T2 to TO have a similar configuration and are connected in parallel to the transmission line 1 via the respective connectors 2.

Transmission and reception operations between the communication units having such a configuration are as follows.

Now, assuming that the communication unit T1 is in the transmitting mode and the other communication units T2 to Tn are in the receiving mode, the light emission of the light emitting element 41 of the photocoupler 51 of the transmitting/receiving section 4 of the communication unit T1 is controlled in accordance with the transmitting signal. be done.

Therefore, the light receiving element 31 is driven on and off according to the amount of light received, and turns the switching element Q on and off. By turning on the switching element Q of the communication unit T1, the second communication unit switches the power supply V of the connection section 3 in its own unit to the resistance R,
→Light emitting element 32→Outbound path of transmission line→Switching element of communication unit T1→Return path of transmission line→Return of power supply V of connection part 3 inside self-supporting unit, forming a closed loop, so that light-emitting device 32 emits light and emitting light outside of self-supporting unit. Receive transmitted signals from.

Similarly, when the communication unit T2 is in the transmission mode and the other communication units are in the reception mode, the switching element Q of the communication unit T2 is turned on and off in response to the transmission signal, and as a result, the same A loop is formed so that the transmitted signal from communication unit T2 is received by the other communication units.

Here, the light emitting element 32 of the photocoupler 52 within one unit of communication in the transmission mode also operates in the closed loop of power supply V→resistance R→light emitting element 32→switching element Q→power return according to the transmission signal of the self-unit unit. Upon formation, its emission is controlled. This light emission state can be used as a monitor signal for the transmission state of its own unit. Signal transmission between each communication unit is performed as described above.

The signal transmission method of the present application is such that no current flows from the power supply V in the connection section 3 of each communication unit to the transmission line when no communication is being performed. It is sufficient to have a capacity, and the required voltage is independent of the number of communication units connected to the transmission line.

Further, since each communication unit is connected in parallel to the transmission line, a communication unit can be freely inserted into or removed from the line without interfering with signal transmission between other communication units. Of course, as in the prior art, the transmission line is electrically insulated from the transmitting circuit and receiving circuit of the communication unit, so there is no influence of other potential differences between the communication units.

Furthermore, in the above-described embodiment, all communication units have been described as having transmitting and receiving functions, but it is clear that they may have only a transmitting function or only a receiving function.

As explained above, according to the signal transmission method according to the present invention, each connection part of each unit has its own power supply,
Since it is connected in parallel to the transmission line, the insertion and removal of any communication unit from the line does not interfere with signal transmission between other communication units.

Further, even if a communication unit that is not in use is in a power-off state, it does not cause any trouble, and furthermore, since there is no need to keep current flowing through the transmission line at all times, power consumption can be reduced.

[Brief explanation of drawings]

FIG. 1 shows a schematic diagram of one embodiment of the invention.

Claims (1)

[Claims] 1 consisting of a pair of transmission lines consisting of an outbound path and a return path, and a plurality of communication units connected in parallel to this transmission line, each communication unit having at least either a signal transmission circuit or a signal reception circuit, and the above-mentioned The transmitting circuit and receiving circuit include
An optical coupling element consisting of a combination of a light emitting element and a light receiving element is provided, and when the optical coupling element is incorporated into a receiving circuit, the light emitting element is connected in series with a power source between the outgoing and incoming paths of the transmission line,
When incorporated into a transmitting circuit, a switching element is connected between the outgoing and incoming paths of the transmission line, and the light receiving element is coupled to the switching element and connected to the transmission line at one end to drive the switching element. A signal transmission method characterized by being connected so that an operating voltage is applied.