Explanation:

Magic tee (or magic T or hybrid tee) :

• The magic tee is a combination of E and H plane tees.
• Arm 3 forms an H-plane tee with arms 1 and 2.
• Arm 4 forms an E-plane tee with arms 1 and 2.
• Arms 1 and 2 are sometimes called the side or collinear arms.
• Port 3 is called the H-plane port, and is also called the Σ port, sum port or the P-port (for "parallel").
• Port 4 is the E-plane port, and is also called the Δ port, difference port, or S-port (for "series").
• A signal injected into the H-plane port will be divided equally between ports 1 and 2, and will be in phase.
• A signal injected into the E-plane port will also be divided equally between ports 1 and 2, but will be 180 degrees out of phase.
• If signals are fed in through ports 1 and 2, they are added at the H-plane port and subtracted at the E-plane port.