R5, R6,& R7 are DPDT relays. R7 is using only one pole, the other available for future use. These three relays are on one stripboard PCB. 12v Aux power passes through R1 coil elsewhere, and the return to ground passes through 2 separate relay switches, R5a & R6a. The idea is that if the 12v Aux fails Then R7a will open and supply will be cut to the relay array. R1 will also switch over. If the 36v supply fails then R5b circuit will switch open, cutting supply to the 6 relay array. If the 18v supply fails then R6b will open and cut the power to the relay array. All this is to prevent the motor going into uncontrolled regenerative braking.