RACEceiver radios are small communication devices which allow officials to talk to all the drivers at the same time. It is generally used to tell drivers the lineup order for restarts after a caution, but also can be used to warn them about accidents or debris on the track.
At AMS, RACEceivers are required for all Cars and Karts in the Adult classes and strongly encouraged for Jr classes. If your driver doesn't have a working RACEceiver, then they'll likely miss the lineup info and be asked to move to the back after a caution.
Our local race shop stocks RACEceivers:
The Race Shack 7532 W Harmont Dr, Peoria, AZ 85345 6232621420
(they are open 8:00 to 3:30 Tue-Fri and 8:00 to 12:00 on Sat)
RACEceivers can also be purchased from nearly all mail order racing supply outlets as well as Amazon