These cost
only a penny each, and, if strict economy is the order of the day, can be
dispensed with should the apparatus not have to be disconnected frequently.
The size of the key is immaterial. The keys made by me have levers 1 inch
wide and 5-1/2 inches long, oak being chosen as material, on account of its
toughness. K is in each case a small wooden knob on a piece of 3/16-inch
brass rod; O a 1-1/2-inch brass screw; A a piece of sheet brass 3-1/2
inches long, marked off carefully, drilled 1/8 inch from the centre of each
end for the pivot screws, and in four places for the holding-down screws,
and bent up at the ends to form two standards. If you do not possess any
brass strip, the lever may be supported on wooden uprights glued and
screwed to the base.
[Illustration: Fig. 34--Telegraphic apparatus mounted on baseboard]
Contact M is a small piece of brass attached to the base by a screw at one
end and by T1 at the other. K was drilled near the end to take the short
coil of insulated wire joining it to T2, and O was similarly connected with
T4.
The spring, S, should be fairly strong.
Pages:
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79