How ETC works
ETC(Electronic Toll Collection System) is a standardized nation wide system.
When passing through the ETC lane of an expressway tollgate, information is passed in both directions between the in-vehicle device that you purchased and installed in advance (with the ETC card inserted) and the roadside antenna. First, the roadside antenna at the entrance tollgate sends a signal to the in-vehicle device with information about the entrance. When exiting the expressway, at the exit tollgate, the in-vehicle device sends the previously-received entrance information to the exit tollgate roadside antenna, the toll is calculated, and the roadside antenna sends toll information to the in-vehicle device.