Configuration doubt

Hi all. I'm new with freeradius. I'd like some help to configure my Radius server, in order to acomplish the following task: I have a radius server, called "R". This radius authenticates users wha want to access our lab equipments, called A, B, C, D and etc. I want to restrict access to these equipments to some users, using radius. For example, user "john" only can access equipments B and C, but can't access equipments A and D. Can anyone help me with this task? Thanks in advance Thiago