An improved vehicle restraint system includes a seat belt tension sensor and an occupant detection control module for characterizing the occupant of a vehicle seat to determine whether to allow or suppress deployment of supplemental inflatable restraints for the occupant. The belt tension sensor includes on-board signal processing circuitry and is coupled to occupant detection control module via a two wire interface that both powers the sensor and its signal processing circuitry and supports communication of belt tension data to the occupant detection control module. The sensor produces an electrical signal responsive to seat belt tension, and the processing circuitry generates one of a specified number of messages pertaining to the range of the measured tension, and then modulates the current through the two wire interface to communicate the generated message to the occupant detection control module.