Relay: A control device that auto-executes the opening and closing of the electric circuit according to changes in the current, voltage, frequency, etc. of another electric circuit.

Reset: The act of restoring the settings of hardware, software, etc. to the specified default values.

REST (Representational State Transfer): REST is an architectural style for distributed systems such as Web. REST interfaces with external systems using HTTP URI, and communicate with HTTP verbs (GET, POST, PUT, DELETE and etc).

Restart: The act of switching off and on by force due to an error related to program execution during device operation.

Ridge: A ridge is a curve that represents a fingerprint, consisting of a continuous curve, an end point where the ridge is cut midway through, and a bifurcation where two ridges meet, which are called minutiae.

RS-485: A standard protocol for serial communication that supports home networking. RS-232 has a low transfer rate and a short transmission range while RS485 enables all devices to transmit/receive data on the same line.