BBC AT/30 Attenuator Panel, 1960. This panel contains two pairs of 600-ohm variable attenuators, each pair covering 0-60 dB in 0.5 dB steps. The input and output of each pair are connected to jacks on the jackfield. The panel also contains a key switch for operating the relay on Relay and Repeating-coil Panel RRC/1.

AT/30 was one of the rack-mounted components used in BBC's AC Test Bay AC/55, a 19-inch bay of equipment for the audio-frequency testing of sound apparatus and the audio-frequency and direct current testing of lines. At small centres where the full facilites were not required the bay was supplied partially equipped as necessary to suit the requirements of the particular station.