TelegraphyLongmans, Green, and Company, 1914 - 422 ページ |
他の版 - すべて表示
多く使われている語句
actual adjustment aerial alternating currents apparatus armature arranged battery Baudot cable capacity cell centre circuit condenser conductor connected copper cord circuit current flowing Daniell cell deflection depressed diameter direction disc disconnected distance duplex earth earth-wire effect electricity electro-magnet electromotive force employed equal fault fixed galvanised galvanometer groove gutta-percha hole indicator inductance induction coil inserted instrument insulation resistance iron wire jack joint K₁ lamp leakage Leclanché cell length lever line wire local battery loop magnet means metal miles milliampères needle negative pole ohms operator ordinary oscillations pair paper perforated pipes placed plug position practice purpose R₁ receiver relay resistance coils reverse rheostat ring rods screw segments sending shown in fig signals soft iron sounder spark gap speed springs station strength subscribers switch tangent galvanometer telegraph telephone terminal total resistance transmitting tube vary vibrations volts Wheatstone Wheatstone Bridge
人気のある引用
102 ページ - B be connected together by an aerial wire, supported at intervals of about 100 yards upon earthenware insulators, then the current which arrives at B from A must necessarily be less than that which leaves A, because at each pole a small portion of the current escapes or leaks to earth. No earthenware support is an absolute insulator. Moisture is deposited upon its surface. The amount of this moisture continually varies, and the resistance of the insulator to the leakage of the current varies with...
48 ページ - The space between parts of the same letter is equal to one dot. 3. The space between two letters is equal to three dots. 4. The space between two words Is equal to five dots. A • B — • • • Period • . . . . . D — . . E . F. ._. ft . I . . K I...
96 ページ - ... equal the polarity induced by the one current must be exactly neutralised by that induced by the other current, for the effects are equal and opposite, and there will be no magnetism excited. Thus, as long as the two circuits are intact, the currents which flow...
154 ページ - Automatic instruments are employed on nearly all long circuits in England, not only because they increase the capacity of the wires for the conveyance of messages, but "because they are so specially adapted for the conveyance of news, which is such a distinctive feature of the English system of telegraphy. One batch of news is often sent to a great many different places, and as four or even eight slips can be prepared at one operation, and one slip can be used several times, the labour of preparing...
v ページ - This text-book, although adapted for the use of students generally, is written specially for those numerous operators and artisans who are employed in the actual transmission of telegrams and in the maintenance of telegraphs in England. Care has been taken to render it as far as possible independent of theory, and of little more than an elementary knowledge of mathematics. The book is intended to serve as an introduction to the study of ^ more advanced works upon the art and science of telegraphy.
138 ページ - Jft are, for repeaters, replaced by transmitters. The adjustment of this apparatus requires great care and great accuracy. Its good working depends essentially on technical skill that can only be acquired by patience and perseverance. Faults in working generally arise from careless adjustments, dirty contacts, loose connections, battery failures, and the ordinary line interruptions, but there are no troubles that are beyond the reach of ordinary skill, and it can be safely said that, within moderate...
97 ページ - B, and that they are operated sometimes by the line current and sometimes by the compensation current. Thus, while A sends messages to B, B can be sending messages to A upon the same wire and at the same time. We assumed that the line current received at A from B was exactly equal to that proceeding from A to B, and that therefore they were exactly neutralised, but it is not so in practice, for owing to the effects of bad insulation the incoming line current is always weaker than the outgoing one....
97 ページ - ... in opposite directions ; but the same effects occur if the opposite poles are to line, and the currents flow in the same direction. If the current from B flows in the same direction as that from A, the effect, when the two stations work simultaneously, is not to weaken the resultant current, but to strengthen it, and therefore to produce a preponderance of the current in wire I over that in wire r of relay E, and, consequently, to register signals ; but in this case the marks made at A, when...