The BC-442 is an antenna control unit in the SCR-274-N Command Radio Set. It switches a common antenna between receivers and transmitters, as well as gives a power indication during transmission. The indicator is important for tuning the transmitters to maximum output.
The unit also has a vacuum capacitor in the rear, for use in series with an antenna which does not naturally resonate with the transmitter frequency.
All connections to the antenna, transmitter, and receiver are external and can be changed easily using built-in binding posts. Control of the unit is paired with the telegraph key/transmission key, so that the antenna is only switched to transmitter when needed. Some units also allow for the pilot/copilot to remotely measure the output meter.