I think this is WBOS's transmitter building, constructed identically to WTKK's on the lower roof level of the Pru. Note the digital radio encoders in the nearest rack. The upper unit, a Broadcast Electronics FSi 10, encodes the audio and auxiliary data streams for transmission; the BE FXi 60 below it is the digital exciter.
Copyright 2004, Garrett Wollman. All rights reserved. Photograph taken 2004-05-06.