General Purpose Transceiver (bottom, grey box) and the Wide Band Transceiver (top, black box)
Image of the general purpose transceiver (GPT) (bottom, grey box) and the wide band transceiver (WBT) (top, black box) on NOAA ShipOkeanos Explorer. This WBT controls the 38 kilohertz frequency and was upgraded from a GPT in 2021.