As you can see in the schematic ... relay switches and now T1 (plus) is connected to contact 2 (and 3) and T2 (minus) is connected to 4 (and 1) therefore the motor is changing the direction of ...

The GRF172 DPDT failsafe relay covers frequencies from DC to 3 GHz. At 2 GHz it delivers a pole to pole isolation of 45 dB and an insertion loss of 0.2 dB. Repeatability of insertion loss is better ...