Telegraph block instrument; block section release with combined bell; Preece's type. Absolute single-semaphore (lower-quadrant/red) block-indicator 2-position/2-indication ("Line Blocked"/"Line Clear"), mounted on a vertical brass-finialled post in a large rectangular brass bezel. Above this is an enamel plate inscribed "Down Line", and below is a brass maker's plate inscribed "Telegraph Works Silvertown London". The blanked-off semi-circular bezel hides redundant signal-information, while above there is in the recessed top of the instrument a blockbell-dome with striker.