A Direct On Line (DOL) starter is an electrical component used to start and control an electric motor. It connects the motor directly to the power supply without the use of a transformer. When the starter is activated, the motor is connected directly to the power source, which causes the motor to start running. This is the simplest method of starting an electric motor and is commonly used for small to medium sized motors. The DOL starter usually consist of contactors and a thermal overload relay, which protect the motor from overloading and overheating.
DOL starters are often used in various industrial and commercial applications such as:
Manufacturing
Agriculture
Mining
Conveyor systems
Pump systems
Compressor systems
 
It is mostly used in applications where a simple and reliable method of starting the motor is required.