A device having a turning point with four bridge branches is fabricated in a double layered film of Ta and Nb by means of photolithographic and anodization techniques. The maximum supercurrent of the device measured at 4.2 K is diffraction modulated by magnetic field. A driving current Id and a bias current Ib are applied to the device in the presence of magnetic field. The critical values of Id at which the voltages appear and disappear across each bridge branch of the device are measured. Various flux quanta propagating states in this device can be obtained by changing Ib. The simplified equivalent circuit of this device is presented. Experimental results are almost explained by a graphical solution of a simultaneous equation which describes the equivalent circuit. The effect of rf radiation (400 MHz) on the dV/dId-Id characteristics of the device is also studied.