I was able to test the two dvstick connected to a raspberrypi.
1. ttyUSB0 config file was set to 2460 service was start successfully.
2. ttyUSB1 config file was set to 2461 service was start successfully.
here are my observation.
if user one using USB0 and user two using USB1 and they are connected at the same time.
when both are using DMR mode one is for example at TG 91 and the other one is on TG 515
both user will hear two talkgroups what ever comes first . which is not supposed to be.
Thanks and 73!