The indicator board is a freestanding structure of 22 vertical panels plus notice boards. The board provided information, particularly the departure time, platform number and station names at which trains would call. It is entirely mechanically operated from floor level and can be divided into three areas for description: the panels, clock faces and platform numbers.
Each of the 22 panels is divided into 30 horizontal pivoting slats, which feature the station name in white letters on a matt black background. Each slat is triangular in cross-section, lettered on one side only and turned by hand via a vertical rod, about 5 mm in diameter, attached at the rear of each slat. The rods attached to slats from the lowest to the highest progressively increase in length and form an arrangement like a series of miniature organ pipes. Station names on one panel are selected by unlocking the small-hinged hatch cover immediately below the slats. When opened, this hatch cover allows all 30 rods to fall simultaneously under their own weight and turns all the slats to the blank position. An adjustable and removable brass template is positioned under the ends of the 30 rods. The template has 30 holes that align with the rod-ends. Each hole may be covered or revealed by a hinged brass flap, one for each hole. Each pair of rod-end and flap represents a station on the line featured on the panel. When the flap is positioned to cover its adjacent hole and the hatch cover is closed, the flap engages its matching rod-end, the rod is raised and the attached slat turns down on the panel, revealing the station name as a stop on the line for that service. When the flap is positioned to expose its adjacent hole and the hatch cover is closed, the matching rod is permitted to pass through the hole in the template and the slat attached to that rod representing a different station remains undisturbed. This means that the station name on this slat is not revealed, indicating that the train will not be stopping there.
The indicator board is divided horizontally and vertically throughout by timber strips decorated with fluting and recessed roundels. At various intervals up the vertical strips between the panels, hooks have been inserted on which extra 'hang on' boards are displayed.
Above the station slats in each panel is a clock face, which features black Roman numerals and hands on a white enamelled background. Each clock face can be set to indicate a train departure time with a key that is inserted into a hole above the station selector tray behind each hatch cover at the base of the slats. The key engages 12 to 1 reduction gears and the movement is taken up to the clock via a rod and worm and worm wheel.
The platform numbers appear in a window set at a slight angle downwards off the vertical and above the clocks on each of the 22 panels. The numbers, finished in white on a black background, are painted onto a continuous roll of canvas that is wound on and off rollers by means of a crank. This is operated from the front of the board at floor level through a hole in the lower panel between the station selector hatch cover and the floor. The cranking movement is taken up to the rollers by a worm and worm wheel at the back of the board and by various gears. The tension is kept on the roll by a suspended counterweight on a separate roller close to each platform roll. Access to the platform roll box is through a removable timber door at the back of each panel.
The main clock at the top of the indicator board is an impulse clock originally operated by an external drive in common with all the other clocks at Central Station to ensure they all kept identical time. It features black Roman numerals and hands set on a white background in a circular brass frame with glass insert.
Towards the end of its working life, four panels were added to the right hand side of the indicator board to provide information on the arrival of trains. Various hang-on boards announced 'Trains From', two rows of clock faces captioned 'Due At' and 'Will Arrive' showed the time, and a last panel signified the platform by means of hang-on boards. The 'arrivals' section of the board was probably added after the previous separate arrivals board was removed.
On either side of the indicator board, supported by decorative wrought iron brackets, are signs giving directions to platforms and electric trains, and a blackboard was available for further notices.
A cast iron barricade with two horizontal rails was erected in front of the board to stop the public from interfering with its operation. Over the years a number of telephones were attached to the lower section of the board. Further objects relating to the board but not attached to it included a set of keys for operating the board, two timber stepladders and a 'Special Notice Board'.