[Milsurplus] B24 and a pair of TR12's

[CL in NC]

First off, I thought the TR12 was a ground based radio for air traffic control.  Does anybody know why B24's were outfitted with a pair of them?  Were they unreliable and needed back up?  I can think of no other WW II military plane that had back up radio gear, some redundant like BC375/BC348 could be supplanted by using the SCR274N, but to have dual equipment meant more weight and less bomb load, or a couple thousand rounds of .50 cal. less.  I have several photos and the full B24 Xray view and it shows a rack with 2 TR12's as big as day.  Asking this due to events concerning B24 LB-30 rebuild.

Charlie, W4MEC in NC