<P> ILS technology delivers two main types of information to pilots . These types include the glideslope (vertical location relative to the designed glide path) and the localizer (lateral position relative to the designed approach course). Each type of information is broadcast using a separate antenna array and each type has a specific critical area: </P> <Ul> <Li> Localizer critical area--aircraft / vehicles / persons or physical obstructions are not authorized in or over the critical area when an arriving aircraft is between the ILS final approach fix and the airport . </Li> <Li> Glideslope critical area--aircraft / vehicles / persons or physical obstructions are not authorized in or over the critical area when an arriving aircraft is between the ILS final approach fix and the airport unless the aircraft has reported the airport in sight and is circling or sidestepping to land on a runway other than the ILS runway . </Li> </Ul> <Li> Localizer critical area--aircraft / vehicles / persons or physical obstructions are not authorized in or over the critical area when an arriving aircraft is between the ILS final approach fix and the airport . </Li> <Li> Glideslope critical area--aircraft / vehicles / persons or physical obstructions are not authorized in or over the critical area when an arriving aircraft is between the ILS final approach fix and the airport unless the aircraft has reported the airport in sight and is circling or sidestepping to land on a runway other than the ILS runway . </Li>

When is the ils hold short in effect