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The best operators cannot send over thirty-five words per minute by hand, but a hundred and twenty words or more per minute can be transmitted by an automatic sender, and the recorder has been found on land lines and short cables to write off the message at this incredible speed. On an ordinary cable of about a thousand miles long, what are electric cables the working speed is about twenty words per minute. It is essential to ensure that the cable cross-section corresponds to the actual requirement and current intensity according to the standards in force. This is where the electrical current flows out from the battery to the vehicle's electrical systems. When the atmosphere is moderately humid, a proper supply of electricity is generated by the mouse-mill, the paper is sufficiently moist, and the ink flows freely. But an excess of moisture in the air diminishes the available supply of exalted electricity. At more temperate places the ordinary means of drying the air by taking advantage of the absorbing power of sulphuric acid for moisture prevailed.

The condensers are merely used to sharpen the action of the current, and render the signals more concise and distinct on long cables. Thus the carrying capacity of the wire is in practice nearly doubled, and recorders are busy writing at both ends of the cable at once, as if the messages came up out of the sea itself. The phase cable is where the electrical current enters, and is the one you must be careful with, given that we are talking about a voltage of 220 or 230 volts. ­Power inverters convert direct current (DC), the power that comes from a car battery, into alternating current (AC), the kind of power supplied to your home and the power larger electronics need to function. Cars without fancy sensors have a low-tech way to tell you that your brake pads need changing: they squeal like angry piglets. Usually, filler materials have been adding between the reinforcing layer and the cable sheath.

But before it reached the Red Sea the cable had broken down, and the instrument was returned dismantled, to be superseded at length by the siphon recorder, in which the marking point is a fine glass siphon emitting ink, and the moving body a light coil of wire hung between the poles of a magnet. Now the tendency of a charged body is to move from a place of higher to a place of lower potential, and consequently the ink tends to flow downwards to the writing-tablet. The ink may, therefore, be electrified to an exalted state, or high potential as it is called, while the body of the instrument, including the paper and metal writing-tablet, are in connection with the earth, and at low potential, or none at all, for the potential of the earth is in general taken as zero. The moving body must be quite free to follow the undulations of the current, and at the same time must record its motions by some indelible mark.

The difficulty of producing such a recorder was, as he himself says, due to a difficulty in obtaining marks from a very light body in rapid motion, without impeding that motion. The marker consisted of a light platinum wire, constantly emitting sparks from a Rhumkorff coil, so as to perforate a line on a strip of moving paper; and it was so connected to the movable needle of a species of galvanometer as to imitate the motions of the needle. The 'duplex' system, or method of telegraphing in opposite directions at once through the same wire, has of late years been applied, in connection with the recorder, to all the long cables of that most enterprising of telegraph companies-the Eastern-so that both stations may 'speak' to each other simultaneously. At Malta a gas flame was used for the same purpose. You can also buy circuit and wire tracers made specifically for the purpose of locating electrical wiring behind walls and underground, often employing radar detection. You can also buy additional cartridges with more songs and games. More recently, the name for electrical safe zones has been altered to ‘prescribed zones’, although you may also see them referred to as ‘permitted zones’.