In a range is the conversion resistance value, and then there is a contact switch, which is the switch of the old TV set and the radio. If there is a fan, there are several gear positions, and several sets of lead wires of the fan winding are connected, and the number of coil turns is changed. To change the speed. The principle is similar to a potentiometer, that is, the potentiometer is usually composed of a resistor body and a movable brush. When the brush moves along the resistor body, a resistance value or voltage which is in a certain relationship with the displacement amount is obtained at the output end.

A rotary switch is a type of switch that controls the opening and closing of the main contact by rotating the handle. There are also two types of rotary switches, namely a unipolar unit structure and a multi-pole multi-position structure. Single-pole unit rotary switches are often used in conjunction with rotary-axis potentiometers in applications, while multi-pole, multi-position rotary switches are often used for switching of operating line.

The common band switch and the shift switch of the universal meter are all rotary switches. There are two kinds of structures: one is the BBM contact type, which is characterized in that when the position is changed, the moving contact is disconnected from the front contact and then turned on. The contact has a state in which it is disconnected from the front and rear contacts.

The other is the MBB contact type, which is characterized in that the movable contact has a state of contact with the front and rear contacts during the transposition. Then disconnect the front contact and keep in contact with the rear contact. In the circuit design, the appropriate rotary switch should be selected according to the circuit application and circuit safety.

Rotary switch, because of its use, the overall use of the sealing structure, has a certain waterproof effect, basically can achieve IP65 waterproof level. At the same time, it is necessary to use a relatively hard and durable metal material, which has the difference of 2 or 3 in the gear position.