BBC D/2 amplifier, 1931. The "First 'D' Amplifier installed in Broadcasting House, 1931", later used at BBC Bristol (number J2132). Full BBC Number: D/2/10. 3 valves are present, 2 valves are missing. Damage to volume control dial scale.
It is a 3-stage rack mounted amplifier with an "echo" output, used to raise the level of transmissions incoming by land-line, such as Simultaneous Broadcast and Outside Broadcast transmissions. The Broadcasting House control room contained a large number of low frequency amplifiers which served to amplify the various transmissions originating in or passing through. These can be divided into four principal types known respectively as A, B, C, and D amplifiers.