may also have more bulbs per set, as they draw somewhat less power per bulb than other incandescent lamps. Control technology Holiday lights can be animated using special "flasher" or twinkle bulbs (usually a red-tipped replacement bulb included with the set) or by electronic controller. Flasher bulbs use a bi-metallic strip which interrupts the circuit when the lamp becomes hot. An electronic holiday light controller usually has a diode bridge followed by a resistor-based voltage divider, a filter capacitor and a fixed-program microcontroller. The micro-controller has three or four outputs which are connected to transistors or thyristor which control interleaved circuits, each with lamps of a single color. Controllers can be set up to change flashing or animation styles by pressing a button or turning a dial on the unit; others have only one pattern, but the speed of this pattern can usually be adjusted by turning a similar dial. Most multi-function sets feature eight to sixteen moving light functions. Some very common functions are fading and chasing. More extravagant and less common functions are stepping on and two-channel flashing. These lights usually come in sets of 140 or 150. This is because to give the chasing effect, bulbs must be arranged in four circuits of 35 (sets of 140) or three circuits of 50 (sets of 150). These light sets use even less power than a regular set of 150, because the lights are not always on, and therefore the bulbs also do not get as hot. Usually, computerized sets cannot be connected end-to-end. However, some newer sets contain special miniature plugs – a female jack is located at the end of the set, and a male plug is located between the control box and the beginning of the actual lights. By disconnecting the control box from one set, it can now be plugged into the end of an identical chasing set to produce a longer strand of chasing lights. These plugs generally have a twist-on locking feature similar to that found on garden hoses. Computer-controlled holiday displays are becoming more and more common today. For instance, a display in Texas uses a PIC microcontroller-based dimmer scheme, and also refers to dimming controllers that people have built based on this scheme. The designs all use mid-range PIC microcontrollers, are generally modular in units of eight channels (dimmable circuits), and use medium-speed, daisy-chainable, one-direction serial communications for input. Most controllers