DPCS in Push-pull trains is done with cables running the entire length of the train, connecting both locos. Wireless communication between the two locos is not being done now, as it does not have sufficient safety clearance.
Wireless DPCS (called DPWCS) is restricted to freight operations for now.
All the trains that are running with push-pull configuration (BBVT Raj, Pune Intercity) have special rakes, which have cables running along the bottom of each coach, to connect both locos.