The button is mounted by screwing the base fast to the door or window casing, it being understood that the wires have been first arranged in place. The button is then set in the hole and the cap is placed over the base, covering it completely. By means of small screws, passed through the rim of the box and into the edge of the base, the cap is held in place. A coat of paint or varnish will finish the wood-work nicely, and this home-made button should then answer every requirement.
Switches and Cut-outs
In electrical equipment and experimental work, switches and cut-outs will be found necessary, particularly so for telegraph and telephone lines. Care should be taken to construct them in a strong and durable fashion, for they will probably be subjected to considerable wear and tear.
A simple switch ([Fig. 5]) is made from a base-block of wood three inches long, two wide, and half an inch in thickness, together with some small metal parts. It has but one contact-point, and that is the brass-headed tack (T in [Fig. 5]) driven through the binding-post, the latter being a small plate of brass, copper, or even tin screwed to the base-block. The end of a wire is caught under the screw-head before it is driven down. A similar binding-post is arranged at the lower side of the block, and the movable arm is attached to it with a screw. Between the arm and the post-plate there should be a small copper washer, to make it work more easily. The arm is cut from a thin piece of hard sheet brass or copper (tin or zinc will also answer very well), and at the loose end the half of a small spool is attached, with a brass screw and washer, to serve as a handle. The end of the screw that passes through a hole in the arm is riveted to the under side to hold it securely in place. This arrangement is shown in [Fig. 6].
The under edges of the arm may be slightly bevelled with a file, so that it will slip up easily on the oval head of the brass tack. The drawing shows an open switch; when the circuit is closed the arm rests on the tack-head. By means of small screws this switch-board may be fastened to a table or to any part of the wood-work in a house.
In [Fig. 7] a complex switch is shown. This is the principle of the shunt-box switch, of the resistance-coil, and also of the commutators of a motor. A motorman’s controller on a trolley-car is a good example of the shunt, and, with it and the resistance-coils, the car can be started, stopped, or run at any speed, according to the current that is admitted to the motor.
The complex switch is made in the same manner as described for the single switch, except that any number of binding-posts may be employed, arranged on a radial plan, so that the end of the arm will rest on any tack-head at will. Bells in various parts of the house may be rung by this switch, or it may be coupled with a series of resistance-coils to control any amount of current.