A vacuum circuit breaker is a device designed for operation as part of electrical high-voltage networks. The name is due to the design feature – a vacuum chamber, due to which instant extinction of the electric arc is achieved. The device is used as switches designed to shutdown equipment in case of emergency. All vacuum circuit breakers can be roughly divided into the following classes:

• Vacuum circuit breakers for 6-10 kV; 
• Vacuum circuit breakers 35 kV; 
• Vacuum switches for 110-220 kV;

A draw-out unit is a unit consisting of a mobile unit and, depending on the function of the cell, respectively: a vacuum circuit breaker, a contact, a block of voltage measuring transformers with fuses, or a short-circuit unit. The trolley makes a mechanical connection between the withdrawable element and the switchgear cubicle. Its stationary part is connected to the cell by means of stoppers on both sides in the guide holes. The trolley makes a mechanical connection between the withdrawable element and the switchgear cubicle. Its fixed part is connected to the cell by means of stoppers on both sides in the guide holes. The moving part of the trolley is moved between the working position and the test position by means of a pulling screw, manually operated by a handle, behind closed doors. The working position and the test position are indicated by the position indicators after the trolley reaches the corresponding position.