A data communications device includes a supervisory circuit, a power supply, and a power circuit. The power circuit includes a data communications port, a power supply connection coupled to the power supply, and a power controller coupled to the data communications port and the power supply connection. The power controller is configured to provide a power signal from the power supply connection to the data communications port in response to communication with the supervisory circuit. Upon loss of communication with the supervisory circuit, the power controller is configured to selectively continue to provide the power signal from the power supply connection to the data communications port when a local parameter has a first value, and discontinue providing the power signal from the power supply connection to the data communications port when the local parameter has a second value.