Power control subsystem for powering a node over communication cabling

1. A power control subsystem for controlling the supply of a power transmitted to at least one node over a communication cabling, the power control subsystem comprising a circuitry to control current of the power transmitted over the communication cabling, said circuitry to control current comprising:

a current sensor arranged to output a signal proportional to the current of the power transmitted over the communication cabling;

a current limiter and switch;

a timer,

a first comparator in communication with said current sensor and arranged to compare the output signal of said current sensor with a first threshold value and output a signal responsive to said comparison, said output signal of said first comparator supplied to said current limiter and switch so as to provide current limiting for the power transmitted over the communication cabling responsive to the first threshold; and

a second comparator in communication with said current sensor and arranged to compare the output signal of said current sensor with a second threshold value, said second threshold lower than said first threshold, said second comparator further arranged to output a signal responsive to said comparison, said output signal of said second comparator supplied to said current limiter and switch via said timer so as to provide delayed over current cut-off of said power at the second threshold.

2. A power control subsystem according to claim 1 , wherein said current limiter and switch is constituted of a single field effect transistor, said single field effect transistor responsive to the output signal of said first comparator in a closed loop arrangement with said current sensor to thereby provide said current limiting for the power transmitted over the communication cabling responsive to the first threshold.

3. A power control subsystem according to claim 1 , further comprising a management and control unit operative to interrogate the at least one node to which it is intended to transmit power over the communication cabling in order to determine whether the node's characteristics allow it to receive power over the communication cabling.

4. A power control subsystem according to claim 3 , wherein said circuitry to control current is responsive to said management and control unit, said circuitry to control current transmitting power to the at least one node responsive to said management and control unit's determination that the node's characteristics allow it to receive power over the communication cabling.

5. A power supply subsystem for providing electrical power to at least one node over a communication cabling, the power supply subsystem comprising:

a means for receiving power;

a means for outputting power for transmission to the at least one node over the communication cabling; and

a circuitry arranged to control current of the power outputted via said means for outputting, said circuitry arranged to control current comprising:

a means for sensing current, said means for sensing current arranged to output a signal proportional to the current of the power outputted via said means for outputting;

a current limiter and switch;

a timer;

a first comparator in communication with said means for sensing current and arranged to compare the output signal of said means for sensing current with a first threshold value and output a signal responsive to said comparison, said output signal of said first comparator supplied to said current limiter and switch so as to provide current limiting for the power outputted via said means for outputting responsive to the first threshold; and

a second comparator in communication with said means for sensing current and arranged to compare the output signal of said means for sensing current with a second threshold value, said second threshold lower than said first threshold, said second comparator further arranged to output a signal responsive to said comparison, said output signal of said second comparator supplied to said current limiter and switch via said timer so as to provide current limiting for said power at the first threshold, and delayed over current cut-off of said power at the second threshold.

6. A power supply subsystem according to claim 5 , wherein said a current limiter and switch is constituted of a single field effect transistor responsive to the output signal of said first comparator in a closed loop arrangement with said means for sensing current to thereby provide said current limiting for the power outputted via said means for outputting responsive to the first threshold.

7. A power supply subsystem according to claim 5 , further comprising a management and control unit operative to interrogate the at least one node to which it is intended to output power for transmission over the communication cabling in order to determine whether the node's characteristics allow it to receive power over the communication cabling.

8. A power control subsystem according to claim 7 , wherein said circuitry arranged to control current is responsive to said management and control unit, said circuitry arranged to control current operative to output power via said means for outputting power responsive to said management and control unit's determination that the node's characteristics allow it to receive power over the communication cabling.