This fitting is used to connect two branch circuits to a single supply line. What is it called?

The choice of "Tee" as the correct answer is based on its design and functionality in a pneumatic system. A tee fitting is specifically engineered to allow two branch circuits to be connected into a single supply line, facilitating the distribution of compressed air or fluid from one source to multiple destinations. This design takes the shape of the letter "T," enabling the proper flow of substances through the branches at a right angle to the main line.

In contrast, the other options serve different purposes. An elbow fitting is used to change the direction of the flow, typically at a 90-degree angle, so it does not function to connect multiple circuits. A male connector is designed for coupling components that primarily fit into female counterparts and does not serve the purpose of branching off to additional circuits. Lastly, a plug is used to seal or close off a fitting rather than connecting multiple lines together. Therefore, the tee fitting is uniquely suited for this specific function in pneumatic systems.