Method and apparatus for multiplexed power and data supply via a two-wire data communication cable

1. An apparatus for supplying power to at least one load device via a two-wire data communication cable, said apparatus being adapted to repeatedly apply a pulsed powering voltage of a predetermined polarity and amplitude for a fraction of time to said two-wire data communication cable, said predetermined amplitude being different from an amplitude of a voltage used for transferring data via said two-wire data communication cable, wherein said predetermined polarity and amplitude of said powering voltage are chosen such that the application of said powering voltage is detected as a collision of data on said two-wire communication cable, and that a distortion of data communication, originating from the application of said powering voltage is handled by a collision detection and arbitration procedure of an applied data communication protocol.

2. The apparatus according to claim 1 , wherein said two-wire data communication cable is a coaxial cable.

3. The apparatus according to claim 1 , wherein a plurality of said load devices are connected to said two-wire communication cable in a bus-type structure and wherein time division multiplexing is applied to share said two-wire data communication cable for power and data transport.

4. A power supply device connected to a two-wire data communication cable, said power supply device comprising an apparatus according to claim 1 .

5. A system comprising:

a. at least one power supply device comprising an apparatus as defined in claim 1 ;

b. at least one load device comprising an apparatus; and

c. a two-wire data communication cable for connecting said at least one power supply device and said at least one load device together in a bus-type structure, wherein at least one end of said two-wire communication cable is powered by said at least one power supply device and wherein at least one end of said two-wire communication cable are terminated by a predetermined termination element.

6. The system according to claim 5 , wherein said power supply device is adapted to repeat application of said powering voltage in a predetermined sequence determined by the characteristics of said power supply device, said two-wire data communication cable and said load device.

7. An apparatus for controlling data transfer and power supply at a load device connected to a two-wire data communication cable, said apparatus comprising a power supply storage part adapted to be recharged when a powering voltage of a predetermined polarity and amplitude is applied to said two-wire data communication cable, and a data transfer part which is adapted to detect on said two-wire data communication cable a temporary drop of a voltage of an amplitude different from said predetermined amplitude in order to receive data, and which is further adapted to generate said temporary drop of said voltage of different amplitude in order to transmit data.

8. The apparatus according to claim 7 , wherein said data transfer part is adapted to transmit data by generating a current sink that pulls low a data signal on said two-wire data communication cable with a predetermined current to create a voltage drop across a termination unit of said two-wire data communication cable, and wherein said data transfer part is adapted to receive data by detecting a voltage drop across a termination unit of said two-wire data communication cable and extracting data from a sequence of pull-down pulses on said two-wire data communication cable.

9. The apparatus according to claim 8 , wherein said termination unit is adapted to limit a current flowing through said termination unit to a value above a predetermined maximum termination current during data transmission but below a predetermined standby current during a powering phase.

10. The apparatus according to claim 7 , wherein said data transfer part is adapted to use Ethernet 10Base2 data arbitration to share said two-wire data communication cable during a data transport phase.

11. The apparatus according to claim 7 , further comprising a decoupling part adapted to decouple said data transfer part from said two-wire data communication cable during a powering phase.

12. The apparatus according to claim 7 , wherein said predetermined polarity and amplitude of said powering voltage are chosen such that the application of said powering voltage is detected as a collision of data on said two-wire communication cable, and that a distortion of data communication, originating from the application of said powering voltage is handled by a collision detection and arbitration procedure of an applied data communication protocol.

13. A load device connected to two-wire data communication cable, said load device comprising an apparatus according to claim 7 .

14. A method of controlling data transfer and power supply to at least one load device, said method comprising:

connecting said at least one load device to at least one power supply device via a two-wire data communication cable in a bus-type structure; and

multiplexing power supply and data transfer via said two-wire data communication cable by applying a voltage of a predetermined polarity to said two-wire data communication cable in order to supply power, and generating at least one temporary drop of a voltage of a polarity opposite to said predetermined polarity in order to transfer data via said two-wire data communication cable.