When the GPO were developing electronic equipment to replace some of the more complex electro-mechanical equipment in telephone exchanges they used glow shifting valves to count dial pulses. These were cold cathode devices with 30 neon electrodes. At night in the dark these units frequently failed until the need for some light was realised. Lighting had to be installed specifically on the racks where dekatrons and other neon based items were installed.
The Dekatron ( produced by Erikssons ) was one of the names of this type of counting device.
