Unit having a power transmission mechanism therein

A unit comprising:

• an input element;
• an output element;
• a first engagement element;
• a second engagement element;
• a third engagement element;
• a first planetary gear mechanism in which a first rotational element being a first sun gear, a second rotational element being a first carrier, and a third rotational element being a first ring gear are arranged in this order on an alignment chart;
• and
• a second planetary gear mechanism in which a fourth rotational element being a second sun gear, a fifth rotational element being a second carrier, and a sixth rotational element being a second ring gear are arranged in this order on the alignment chart, wherein
• the input element is connected to the first rotational element and the sixth rotational element,
• the output element is connected to the second rotational element,
• one side of the first engagement element is connected to the third rotational element and the fifth rotational element,
• the other side of the first engagement element is fixed,
• one side of the second engagement element is connected to the fourth rotational element,
• the other side of the second engagement element is fixed, and
• the third engagement element connects two rotational elements that are selected from the first to sixth rotational elements and are not connected to each other.