69
48. Push button 70
49. Electric bell 71
50. Armature of electric bell 72
51. Vertical section of annunciator 72
52. Front view of annunciator 72
53. Horizontal section of annunciator 72
54. Front plate of annunciator 72
55. Alarm switch on window 76
56. Burglar alarm on window 76
57. Burglar alarm contact 77
58. Neutral position of contact 78
59. Circuiting for electric bell 79
60. Annunciators in circuit 80
61. Wiring system for a house 80
62. Accumulator grids 83
63. Assemblage of accumulator grids 85
64. Connecting up storage battery in series 87
65. Parallel series 88
66. Charging circuit 88
67. Telegraph sending key 91
68. Telegraph sounder 92
69. A telegraph circuit 94
70. Induction coil and circuit 99
71. Illustrating elasticity 100
72. Condenser 101
73. High-tension circuit 102
74. Current interrupter 103
75. Wireless-telegraphy coherer 105
76. Wireless sending-apparatus 107
77. Wireless receiving-apparatus 108
78. Acoustic telephone 111
79. Illustrating vibrations 111
80. The magnetic field 112
81. Section of telephone receiver 114
82. The magnet and receiver head