=S-W-G.= An abbreviation for standard wire gauge. =Switch.= A device for opening and closing an electric circuit. Made in a great variety of forms, such as push-button, telegraph-key, knife switch, automatic switch, lever switch, rheostat, etc. =Switch-bell.= A combined bell and switch. The bell is operated when the switch is opened or closed. =Switch-blade.= The blade of a switch; a conducting strip connecting two contact-jaws. =Switch-board.= A board or table to which wires are led and connected with cross-bars or other devices by which connections can be made. =Synchronize.= To agree in point of time; to effect concurrence of phase in two alternating-current machines, in order to combine them electrically. T =Table-push.= A push-button connected with a call-bell and fixed on a table for convenience in using. =Tamadine.= A form of cellulose used for making the filaments of incandescent lamps. The material is cut into proper shapes, carbonized, and flashed. =Tangent Galvanometer.= (_See_ Galvanometer, Tangent.) =Tape, Insulating.= Prepared tape used in covering the bared ends of wires or joints. =Tap-wires.= The conductors in trolley systems that at stated intervals, take the current from the mains and supply it to the bare feed-wires. =Telegraph.= A system of electric communication invented by S. F. B. Morse, in which the dot-and-dash characters are used. There are various modifications of the system--double (or duplex), multiplex, and quadruplex--by means of which a number of messages may be sent out over the same wires at one time. Communication from place to place is had over wires mounted on poles, or by underground or submarine cables. =Telegraphy, Wireless.= A system of telegraphy carried on without the aid of wires, using instead the ether waves of the atmosphere to conduct the vibrations overhead, and the ground, or earth, as a return. The present limit of its working is about four thousand miles. =Telephone.= An instrument and apparatus for the transmission of articulate speech by the electric current. A magnet is encased in a tube and is encircled at one end by a coil of fine, insulated wire. A diaphragm of thin iron is fixed in front of the coil and close to the end of the magnet. The ends of the coil-wires are connected with a line, at the other end of which another and similar instrument is installed. The voice causes the sending diaphragm to vibrate, and these waves are transmitted to the other instrument, where they can be heard through contra-vibrations of the receiving diaphragm. =Telephone, Long-distance.= A telephone of modern construction, in which the sound-recording mechanism is so sensitive as to make the vibrations of the voice audible at long distances. It will work satisfactorily at one thousand or even fifteen hundred miles. =Terminal.= The end of any open electric circuit, or of any electric apparatus, as the electrodes of a battery.