278.3 and 351.9 at St Louis International Airport

[zerg901]

AirNav: KSTL - St Louis Lambert International Airport - 278.3 and 351.9 listed as PRM - I believe the aircraft puts a 2nd radio receiver on 1 of these 2 freqs when doing simultaneous ops on parallel runways - aircraft listens for alerts from control tower - but no civilian freqs listed for PRM - ???

 

[zerg901]

https://www.faa.gov/training_testing/training/prm/media/PRM_training.pdf - FAA document that explains PRM