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.