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.

RF(Radio Frequency): The frequency used to recognize information at close range or from a distance.

RFID: Short for Radio-Frequency Identification, this is a technology whereby IDs are recognized using RF(Radio Frequency). This technology allows you to store information in an RFID Tag composed of an antenna and a chip and identify information by reading it with an RFID reader.

RFID Tag: An electronic tag attached to an object such as a card in order to store the unique identification information of a person or object. An RFID reader wirelessly recognizes the information stored in an RFID tag using radio waves. An RFID tag generally consists of a small processor, a memory, a small antenna, a battery, and so on. RFID tags are divided into various types depending on their capability to read/write, the presence of a built-in battery, and the RF(Radio Frequency) band, etc.

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.