Sequencers are not a specific brand but a category of industrial control devices used to automate processes by controlling the sequence of operations. They are commonly used in industries like manufacturing, energy, and automation. Companies such as Siemens (Germany), Allen-Bradley (a brand of Rockwell Automation, USA), and Schneider Electric (France) produce sequencers as part of their industrial control product lines. These devices are essential for applications requiring precise timing and order of operations, such as conveyor systems, batch processing, and machinery control.