The devices used for giving the flashing and changeable effects to electric lights in any form are called "flashers." The mechanism may be constructed to flash a sign by spelling the words out, one letter at a time, flashing border lights around a window, changing colors in glass signs, or in fact in any way to attract the eye.
There are two advantages in favor of using a flasher: 1, it causes the passerby to look at the sign, and 2, reduces the cost of electricity, because the lamps are switched off periodically.
There are numerous kinds of flasher, and they may be classified, according to construction of the switch contacts, as:
1. Carbon type;
2. Brush type;
3. Knife type.
Again, with respect to operation or the electrical effects, they may be classified as
1. Simple on and off flashers;
2. High speed flashers;
3. Lightning flashers;
4. Script breakers;
5. Chaser flashers;
6. Thermo flashers;
7. Carriage calls;
8. Talking signs;
9. Electric clocks.
Fig. 1,011—Dull's carbon type flasher. This is a main line flasher; that is, it is set into the main wires instead of carrying down each circuit. The circuits are opened and closed on carbon contacts, reinforced with standard knife switches. The blades are opened and the current broken by gravity alone. Each switch can be made to hold the lights for any period from 18% to 81% of a revolution of the shaft. They can throw on the circuits progressively or all on and all off together. Again, the circuits may be closed progressively, remain on a few seconds, and then be opened progressively. No circuit or circuits can be closed more than once per revolution.
Carbon Flashers.—In this type of flasher, carbon breaks are provided, that is, the arc which is formed when the circuit is broken, falls on carbon, while metal switches are provided to carry the load. Thus the carbon gets the arc which prevents the switches burning, while the switches carry the load to prevent the carbons becoming heated and disintegrated. The carbons must be adjusted occasionally according to the load they are carrying. Carbon machines are made either double, triple, or series break.