=Reduction.= The influence exerted without apparent communication by a magnetic field or a charged mass upon neighboring bodies. The induction-coil is a simple example of this force. The current passes through the primary or inner coil about a core of soft iron, and in doing so it develops lines of force in the secondary or outer coils, although no current is flowing directly through them from a battery or dynamo. =Reduction Gear.= A gear which acts to reduce a speed below that of a motor in full motion without lessening its motive force. =Refract.= To break the natural course of light in an elastic medium. The rays of light, as they pass from a rare into a dense medium, are refracted. =Register, Electric.= An apparatus for registering and recording the movements of employés about a building. Press-buttons are arranged throughout the building, and when a man passes a station he presses the button, and the time is recorded by the apparatus. =Regulator Magnet.= (_See_ Magnet, Regulator.) =Relay.= A telegraphic or telephonic receiving instrument which opens and closes a local circuit through movements caused by the impulses of currents received. The relay battery may be very delicate so as to work with weak currents. The function of the relay is to open and close circuits for the admission of a new current to push on the sound or vibration to a more distant point. The main battery may be of any desired power. =Relay Connection.= A connection used in telegraphy, including a local battery, with a short circuit, normally open, but closed at will by a switch and sounder, or other appliance. A very weak current will work the apparatus. =Relay, Ordinary.= A relay that is not polarized. =Relay, Repeating.= In telegraphy, a relay for repeating the signals through a second line. =Reluctance.= Magnetic resistance. =Repeater.= In telegraphy, an instrument for repeating the signals through a second line. It is virtually a relay which is controlled by the sender, and which, in turn, operates the rest of the main line. It is usually located at about the middle of the total distance covered. =Repeating-station.= A telegraph station located on a long line, and occupying a position at the juncture of the sections into which the line is divided. The currents received through one section are repeated into the other sections by means of a repeater. =Repulsion, Electric.= The tendency which exists between two bodies charged alike to mutually repel each other. =Residual Charge.= (_See_ Charge, Residual.) =Resilience.= The power to spring back to a former position. Electricity is resilient, although its elasticity cannot be measured accurately.