Inside an operating ANITA Mk VIII (aka Mk 8) electronic calculator, which together with the Mk VII were the world's first electronic desktop calculators when launched in 1961.

This photograph shows:

• The display on the right with a dozen nixie-type numerical indicator tubes, each mounted on the edge of a counter board.
• The daughter boards in the centre holding many cold-cathode switching tubes. Some of these are lit up (like neon lamps, to which they are related), which shows that they are in the "on" state.
• A GS10D Dekatron decade counter tube at top left (with a red mark on top), which is used to scan the keyboard for pressed keys.
• Two ECC81 double-triode vacuum tubes, or thermionic valves, to the right of the Dekatron.
• Many selenium diode packs, which are the black rectangular blocks.

Warning: there are dangerously high voltages exposed when operating one of these machines like this with the covers open.