I am trying make a network of RS485 using around six arduino NANO as slave and PC as Master. I have purchased six TTL to RS485 converter and one RS485 to USB module. The TTL modules show 120ohm resistance when I measure before connecting at its A & B points. But the RS485 to USB module shows open resistance( No value). I want to know whether it doesnot have the terminating resistance and pull up and pull down resistance as it is seen in TTL-RS485 modele as R5,R6,R7 ? Should I remove R5-6-7 resistance from all modules excepting the end module?