||1. Interrogator: Primary radar relies on a signal being
transmitted from the radar antenna site and for this signal to be
reflected or bounced back from an object (such as an aircraft).
In the ATCRBS, the Interrogator, a ground-based radar beacon transmitter-receiver,
scans in synchronism with the primary radar and transmits discrete
radio signals which repetitiously requests all transponders, on the
mode being used, to reply.