After exhausting and capping, the tubes were fitted with their bases and still in their linen bags, were transferred onto a conveyor belt where each tube was plugged into an adaptor which supplied the appropriate voltages to the heater, cathode, grid and first anode as well as a heat from an embedded element which baked the cement inside the base cap thus hardening and attaching the base to the bulb neck: -

After heating and as power was applied to the tube, the heater fired and cathode emission commenced and this initial 'firing' reduced a part of the cathode material from the oxide form back to metallic Strontium and Barium which increased the cathode's emissive properties.    Once the fired tube reached the end of the conveyer belt, it was transferred to one of the test benches where it received an intensive check under true operating conditions as you can see from the photo below: -