JPS6338134B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an information signal transmission device in a system that converts measurement information and the like into signals and transmits them via a cable.

When information is converted into a signal and transmitted via a cable, reflected waves are generated due to mismatching between the transmitting device or the receiving device and the cable, and as a result, the signal may not be transmitted correctly.

As a countermeasure against this, as shown in FIG. A method of absorbing reflected waves by supplying a specified voltage from power supplies 8, 9, 10, and 11 via terminals 6 and 7 is well known. In this method, in order to effectively absorb reflected waves, the power supplies 8, 9, 10, and 11 have low internal impedances of several ohms or less.

However, for example, the power supplies 10 and 11 of the receiving device R
When the power goes out, the voltage of the power supplies 10 and 11 becomes zero, and the power supplies 10 and 11 become equivalent to impedance elements of several ohms or less. Therefore, the unidirectional elements 6 and 7 of the receiver R are in the same state as if they were grounded with an impedance of several ohms or less.

If the transmitter S sends a signal to the receiver R in such a state, the receiver is overloaded, so the diodes 6 and 7 of the receiver R or the transmitter circuit 1 of the transmitter S Excessive current may flow through the device and cause a malfunction. In addition, two or more transmitting devices can be connected in multiple ways on the receiving side and combined into one.
Correspondingly, in a system that has one receiving device, if one transmitting device is out of power and sends a signal from another transmitting device, one direction of transmission during the power outage will occur due to the same reason as mentioned above. In some cases, the transmission element or the transmission circuit of the transmitting device that sent the signal may fail. To prevent this, in conventional devices, for example, in the event of a power outage, the device and the cable are separated so that the transmitting circuit 1, the cable 3, and the cable 3 are disconnected.
A switch 1, such as a relay contact, which opens in synchronization with a power outage, is connected between the receiver circuit 2 and the receiver circuit 2.
2,13 was inserted to protect the device.

However, in this conventional method, a switch such as a relay contact is inserted into the transmission line through which the signal passes, which has the disadvantage of impairing the transmission quality of the signal. This is a problem that cannot be ignored, especially when transmitting low-level high-frequency signals. Furthermore, when a plurality of circuits are housed in one equipment rack, as many switches as the number of circuits to be housed are required, and it has been desired to reduce the number of switches.

An object of the present invention is to provide an information signal transmission device that eliminates such conventional drawbacks.

The present invention avoids inserting a switch in the transmission path, and replaces the conventional connection between the unidirectional element provided for absorbing reflected waves and the power supply supplied to the element with a constant connection to the power supply. This introduced the concept of opening and closing depending on the state of the air.

FIG. 2 shows one embodiment of the present invention, with unidirectional elements 4, 5, 6, 7 and corresponding power supplies 8, 9, 1.
Switches 14, 15, 16, 1 between 0 and 11
7, and power supply 8, 9, 1 depending on the cause of power outage etc.
When at least one of 0 and 11 is out of the specified voltage range, the voltage monitoring means (not shown) that was monitoring the power supply detects this and detects the power supply that is out of the specified voltage range. The switch connected to the power source is opened or placed in a high impedance state, and the unidirectional element connected to the power source is opened from the power source to prevent the cable 3 from being grounded with low impedance.

According to the present invention, even if the power is cut off due to a power switch operation, a power outage, or a power failure occurs, the sending end of the transmitting device or the receiving end of the receiving device will not be overloaded, so that the other party's or own device In addition, since no switch is inserted into the transmission path unlike conventional devices, the transmission quality is improved. Furthermore, even when multiple circuits are housed in one equipment rack as shown in Figure 3, power can be supplied through one set of switches commonly provided in one equipment rack, so there is less power per equipment rack. One set of switches is sufficient regardless of the number of circuits accommodated in the circuit, and the reduction in the number of used elements has the effect of increasing economy and reliability.

[Brief explanation of the drawing]

FIG. 1 shows a conventional embodiment, FIG. 2 shows an embodiment of the present invention, and FIG. 3 shows another embodiment of the present invention. In the figure, S is a transmitting device, R is a receiving device, 1
is the transmitting circuit, 2 is the receiving circuit, 3 is the cable, 4,
5, 6 and 7 are unidirectional elements, 8, 9, 10 and 11 are power supplies, 12, 13, 14, 15, 1
6 and 17 indicate switches.

Claims (1)

[Scope of Claims] 1. One or more transmitting circuits, one or more receiving circuits, independently provided at each of the transmitting end of each said transmitting circuit and the receiving end of each said receiving circuit, A plurality of unidirectional elements each having one end connected to the sending end or the receiving end, and one unidirectional element for each power source between the power source common to the transmitting circuit and the other end of the unidirectional element of each transmitting device. a switch provided for each power source between a power source common to the receiving circuit and the other end of the unidirectional element of each receiving device; and a switch that monitors the voltage of each power source. , a voltage monitoring means that detects when the voltage of any power supply goes out of a specified range and opens or puts the switch connected to the power supply whose voltage has gone out of the specified range into a high impedance state; An information signal transmission device comprising: