The module is a part of the FST-1 Coordinate Data Transmitter that sent the radar data from the Mt. Baldhead Gap Filler Radar Station down phone lines to the Fort Custer Direction Center in Battle Creek. The module was part of the first radar digital signal processing unit and first modem used in an actual application. From the radar cabinet panel from the SDHC Cold War/Hot Towns exhibit (2017-18): "This FST-1 power supply cabinet was removed from the Mt. Baldhead Gap Filler Radar Annex in the 1980s. It includes components from the AN/FST-1 Coordinate Data Transmitter. The FST-1 sorted radar data to distinguish legitimate targets and transmitted the radar data down telephone lines in the first-ever use of a modem outside a research environment. The heart of the AN/FST-1 was a RCA 6499 Radechon barrier grid tube, a state-of-the-art memory device which, like the modem, was made available mere months before deployment in the FST-1."

7 in

1/2 in

4-1/4 in