=Bridge.= A special bar of copper connecting the dynamos with the bus wire in electric lighting or power stations. =Bronzing.= The deposition of bronze by electro-plating methods. The mixture is of copper and tin, and a cast bronze plate is used as an anode. =Brush.= A term applied to the pieces of copper, carbon, or other conducting medium in dynamos and motors, that bear against the cylindrical surface of the commutators to collect or feed in the current. =Bug.= Any fault or trouble in the connections or workings of an electrical apparatus. The term originated in quadruplex telegraphy, and probably had some connection with the Edison bug-killer that he invented when a boy. =Buoy, Electric.= A buoy to indicate dangerous channels in harbors and to mark wrecks and reefs. It is provided with an electric light at night, and with a gong or an electric horn by day. =Burner, Electric.= A gas-burner so arranged that the flame may be lighted by electricity operated by a push-button at some distance from the fixture, or, close at hand, by means of a chain or pull-string. =Burning.= In a dynamo, the improper contact of brushes and commutator, whereby a spark is produced and an arc formed which generates heat and causes the metal parts to burn. =Bus-rod.= A copper conductor used in power-plants to receive the current from the battery of dynamos. The distributing leads are connected to these rods. =Butt-joint.= A joint made by bringing the ends of wires together so that the ends butt. They are then soldered or brazed. =Button, Electric.= A form of switch that is operated by pushing a button mounted on a suitable base. Used principally for ringing bells, operating lights, etc. =Buzzer.= An electric alarm, or call, produced by the rapid vibration of an armature acted upon by electro-magnetism. The sound is magnified by enclosing the mechanism in a resonant box. An apparatus resembling an electric bell _minus_ the bell and clapper. The buzzer is used in places where the loud ring of a bell would be a nuisance. C =C.= An abbreviation for centigrade when speaking of thermal temperature. In chemistry the centigrade scale is used extensively, but in air temperatures the Fahrenheit scale is universally employed. =Cable, Aerial.= A cable that contains a number of wires separately insulated, the entire mass being protected by an external insulation. It is suspended in the air from pole to pole, and sometimes its weight is so great that a supporting wire is carried along with it (usually overhead), the large cable being suspended from it by cable-hangers. =Cable Box=. A box to receive cable ends and protect them; also, the box in which cable ends and line-wires are joined. Submarine cable boxes are usually near the ground, while telephone and telegraph cable boxes are mounted on poles, the cables running from the ground and up the poles to the boxes.