A ring hybrid is commonly used as a signal combiner/splitter and phase shifter.

Power Splitting

When power is input to the Sum port, it splits equally between Ports 2 and 3 in phase. Alternatively, when power is input to the Difference port, it splits between Ports 2 and 3 with a 180-degree phase shift.
 
 Power Combining
 As a power combiner, input power at Ports 2 and 3 will result in the sum of the signals at the Sum port, while the difference appears at the Difference port.