A two-conductor hard-wired communications link accepts a value of at least one parameter from an environmental sensor in the form of data encoded on the conductors via current modulation. The sensor can be mounted in a location remote from a controller. A circuit connected to the sensor transmits an RF signal representing the value of the parameter detected by the sensor. A data relay connects to the hard-wired communication link of the controller. The data relay includes a receiver that receives the RF signal, and circuitry configured to extract the value of the parameter and to emulate a set of physical and protocol properties of the hard-wired communication link of the controller.