Switches are the control consisting of a mechanical or electrical or electronic device for making or breaking or changing the connections in a circuit. They contribute every step of the electric world. Pushbutton switches are used in military, medical, telecommunications, test and measurement equipment, electric linear actuators and controls. Multiway switching is a method of connecting switches in groups so that any switch can be used to connect or disconnect the load. This is most commonly done with lighting. Intermediate switches are also an important part of multiway switching systems with more than two switches. A DPDT switch has six connections, but since polarity reversal is a very common usage of DPDT switches, some variations of the DPDT switch are internally wired specifically for polarity reversal. Switches can be classified according to the arrangement of their contacts. Some contacts are normally open until closed by operation of the switch, while others are normally closed and opened by the switch action. A switch with both types of contact is called a changeover switch. The simplest form of switch is the knife switch. Biased switches are one containing a spring that returns the actuator to a certain position. Placing parentheses around all positions other than the resting position can modify the "on-off" notation. The momentary push-button switch is a type of biased switch. DIP switches are ideal for applications in telecommunications, network, computer and peripheral equipment, control, security, alarm, and instrumentation. Encoder switches have applications in medical, avionics, transportation equipment, fitness equipment, commercial, test and measurement equipment, and PC-based factory automation. Rotary switches are ideal for navigation, communication equipment for the avionics industry; precision measurement gauges, commercial sound mixing and editing consoles, military voice and data communications, radios, transmitters and receivers. Keyboard and keypad switches ideal for computer and telecommunications equipment, instrumentation, control panels, POS terminals and recreational vehicles. Tact switches have wider applications such as consumer electronics, audio equipment, PCs, VCRs, modems, communications equipment, controls, security and alarm equipment. A wide range of switches are available like joystick, leaf, light operated ability switch, low pressure, muscle twitch, no contact, pushbutton, rocker, sip and puff, tilt, wobble, tact etc.