An apparatus comprising: a conductor to enable the apparatus to be coupled to a two-way communications device; a voltage sensor coupled to the conductor to measure a voltage present on the conductor relative to a ground conductor; a controller coupled to the conductor, and structured to: monitor the conductor for a first end to a first instance of signal activity occurring on the conductor; characterized in that the controller is further structured to: in response to the first end, inject a current into the conductor and operate the voltage sensor to obtain a first measure of a voltage on the conductor while the current is injected into the conductor; calculate an adaptive threshold voltage from at least the first measure; monitor the conductor for a second end to a second instance of signal activity occurring on the conductor; in response to the second end, inject a current into the conductor and operate the voltage sensor to obtain a second measure of a voltage on the conductor while the current is injected into the conductor; compare the second measure to the adaptive threshold; and in response to the second measure being greater than the adaptive threshold, turn off a component of the apparatus. a conductor to enable the apparatus to be coupled to a two-way communications device; a voltage sensor coupled to the conductor to measure a voltage present on the conductor relative to a ground conductor; a controller coupled to the conductor, and structured to: monitor the conductor for a first end to a first instance of signal activity occurring on the conductor; monitor the conductor for a first end to a first instance of signal activity occurring on the conductor; characterized in that the controller is further structured to: in response to the first end, inject a current into the conductor and operate the voltage sensor to obtain a first measure of a voltage on the conductor while the current is injected into the conductor; calculate an adaptive threshold voltage from at least the first measure; monitor the conductor for a second end to a second instance of signal activity occurring on the conductor; in response to the second end, inject a current into the conductor and operate the voltage sensor to obtain a second measure of a voltage on the conductor while the current is injected into the conductor; compare the second measure to the adaptive threshold; and in response to the second measure being greater than the adaptive threshold, turn off a component of the apparatus. in response to the first end, inject a current into the conductor and operate the voltage sensor to obtain a first measure of a voltage on the conductor while the current is injected into the conductor; calculate an adaptive threshold voltage from at least the first measure; monitor the conductor for a second end to a second instance of signal activity occurring on the conductor; in response to the second end, inject a current into the conductor and operate the voltage sensor to obtain a second measure of a voltage on the conductor while the current is injected into the conductor; compare the second measure to the adaptive threshold; and in response to the second measure being greater than the adaptive threshold, turn off a component of the apparatus.