Data communication system

• US 20040042419A1
• Filed: 03/04/2003
• Published: 03/04/2004
• Est. Priority Date: 03/05/2002
• Status: Active Grant

• Current Assignee: Furukawa Electric Company Limited
• Original Assignee: Furukawa Electric Company Limited
• Inventors: Hara, Shoji, Ichii, Eiji
• Granted Patent: US 7,302,184 B2
• Time in Patent Office: Days
• US Class Current: 370/278
• CPC Class Codes: H04B 2203/5458 Monitor sensor; Alarm systems
• CPC Class Codes: H04B 2203/547 via DC power distribution
• CPC Class Codes: H04B 3/548 the power on the line being DC arrangements for feeding power H04L12/10; extracting feeding power from signals H04L25/02

Abstract

A data communication system comprising a terminal unit for generating light signals responsive to status of switches and a control unit for receiving the signals spatially propagated and controlling operation of a predetermined load, wherein switches 11 and 12 are interposed between plus and minus lines 51 and 52 as power lines for supplying electric power from the control unit to the terminal unit, and connected in series with respective resistors R1 and R2 having different values of resistance, and the minus line is grounded in the control unit 30 through resistor R0. Potential of the minus line changes in response to switches 11 and 12, and electronic signals indicative of the status of the switches are transmitted to the control unit separately from the light signals. Thus, even if the spatial propagation of the light signals is interrupted, the control over the operation of the load is secured.

Claims

1. A data communication system comprising a terminal unit for generating signals responsive to status of a plurality of switches, a control unit for controlling operation of a predetermined load according to the signals transmitted from the terminal unit, and power supply lines for supplying power supply required for operation of the terminal unit from the control unit to the terminal unit, the data communication system wherein:

the terminal unit comprises light signal-transmitting means for generating light signals according to operation of the switches and spatially propagating the light signals to the control unit, and electronic signal-transmitting means for generating electronic signals according to the operation of the switches and transmitting the electronic signals to the control unit through the power supply lines, and wherein;

the control unit comprises light signal-detecting means for detecting the light signals transmitted by the light signal-transmitting means and controlling the operation of the load, and electronic signal-detecting means for detecting the electronic signals transmitted by the electronic signal-transmitting means through the power supply lines and controlling the operation of the load when the transmission of the light signals from the terminal unit is discontinued.

2. The data communication system according to claim 1, wherein:

the power supply lines comprise a plus and a minus line for supplying DC power from the control unit to the terminal unit, the minus line being grounded in the control unit through a first resistor, and wherein;

the electronic signal-transmitting means located in the terminal unit comprises a plurality of second resistors having different values of resistance, the second resistors being connected in series to the respective switches, and series circuits of the respective switches and the respective second resistors are interposed between the plus line and the minus line, respectively.

3. The data communication system according to claim 1, wherein:

the power supply lines comprise the plus and minus lines for supplying the DC power from the control unit to the terminal unit, and an exclusive line for supplying a predetermined voltage to the terminal unit through the first resistor in the control unit, and wherein;

the electronic signal-transmitting means located in the terminal unit comprises the second resistors having the different values of resistance, the second resistors being connected in series to the respective switches, and the series circuits of the respective switches and the respective second resistors are interposed between the exclusive line and the minus line, respectively.