The change in voltage or current of the antenna is measured by the time to reach a particular voltage level. Using either charging and/or discharging, the times to reach two or more different levels of the total charge are measured. By providing sensor electronics with each sensor or antenna, a more versatile system may be provided. The sensors and associated electronics communicate using a bus or other communication path to a processor. The processor determines an occupant state based on the received sensor information. Different numbers of sensors may be used with the same system.