Abstract: A transponder of an interrogator and toll highway system has a non-electronically activated switch for a first state in which the transponder is in an “active” mode and a second state in which the transponder to be in an “inactive” mode. A non-electronic hanging device hangs the transponder in a vehicle for receiving interrogating signals and a non-electronic activator causes the switch to be in the first state only when the transponder is placed within the hanging device, and to be in an “inactive” mode when the transponder is not placed within the hanging device.