Method of monitoring the powering of a remote device through a lan line and relative circuit

A method of monitoring powering of a device through a local area network (LAN) connection comprising:

• applying a time-varying voltage to a second terminal of the LAN connection through a de-coupling capacitor while powering the device by applying a DC voltage to a first terminal of the device;
• sensing a time-varying voltage on the second terminal caused by the applied time-varying voltage;
• and
• continuing powering of the device with the DC voltage based upon at least one electric parameter of the sensed time-varying voltage.

A method of monitoring powering of a device through a local area network (LAN) connection comprising:

• applying a non-negative time-varying voltage to a second terminal of the LAN connection through a de-coupling capacitor while powering the device by applying a DC voltage to a first terminal of the device;
• sensing a time-varying voltage on the second terminal caused by the applied non-negative time-varying voltage;
• continuing powering of the device with the DC voltage based upon at least one electric parameter of the sensed time-varying voltage;
• and
• comparing an amplitude of the sensed time-varying voltage with a threshold voltage, and stopping powering of the device with the DC voltage when the threshold voltage is exceeded.

A circuit for generating a flag signal indicative of whether a device is powerable through a local area network (LAN) having first and second terminal comprising:

• a DC voltage generator configured to apply a DC voltage to the first terminal;
• a time-varying voltage generator;
• a decoupling capacitor to couple the time-varying voltage generator to the second terminal of the LAN;
• a comparator configured to compare a sensed time-varying voltage on the second terminal with a threshold and to generate a flag based thereupon;
• and
• a switch to ground the second terminal based upon the flag.

A circuit for monitoring powering of a device through a local area network (LAN) connection having first and second terminals comprising:

• a voltage generator coupled to a de-coupling capacitor and configured to apply a time-varying voltage to the second terminal;
• a DC voltage generator configured to power the device with a positive DC voltage applied to the first terminal while the voltage generator applies the time-varying voltage to the second terminal;
• a comparator configured to sense a time-varying voltage on the second terminal;
• and
• a switch configured to continue powering of the device by the DC voltage based upon at least one electric parameter of the sensed time-varying voltage.