=Cable-core.= The conductors of a cable which make up its interior mass. For the convenience of linemen the wires are often insulated with different-colored materials so that testing is not necessary when making connections. =Cable-hanger.= A metallic grip, usually of sheet metal, arranged to clasp two or more wires. It is fastened to the supporting wire by a hook and eye, or by small bolts with thumb-nuts. =Cable-head.= A rectangular board equipped with binding-posts and fuse wires so that the connections may be made between the cable ends and the overhead or line-wires of a system. =Cables.= An insulated electric conductor of large diameter, often protected by armor or metallic sheathing, and generally containing, or made up, of several separately insulated wires. Cables supply current to traction lines; power, through subterranean passages; communication, by submarine connection; and light, by overhead or underground conduits. =Call-bell.= A bell that is rung by pressing a button, and which is operated by electricity. =Calling-drop.= A drop-shutter which is worked by electricity in a telegraph or telephone exchange; it denotes the location from which the call was sent in. Small red incandescent lamps have taken the place of the drops in most of the large telephone exchanges, for they are noiseless and do not annoy the operators as the drops and buzzers did. =Candle-power.= The amount of light given by the standard candle. The legal English and American standard is a sperm candle burning two grains a minute. =Candle, Standard.= The standard of illuminating power; a flame which consumes two grains of sperm wax per minute, and produces a light of a brightness equal to one candle-power. =Caoutchouc.= India-rubber. So named because originally its chief use was to erase or rub off pencil marks. It is a substance existing, in a thick fluid state, in the sap or juices of certain tropical trees and vines; it possesses a very high value as an insulator for wire and circuits. The unworked, crude rubber is called virgin gum, but after it is kneaded it is called masticated or pure gum rubber. =Capacity.= A term used when speaking of the carrying power of a wire or circuit. The capacity of a wire, rod, bar, or other conductor is sufficient so long as the current does not heat it. Directly electric heat is generated, we speak of the conductor as being overloaded or having its capacity overtaxed.