Does anyone remember these tubes from the late 60's early seventies. Used alot in electronic scales and pinball machines. They are made of 7 segmented filaments that run on about 4 volts. These are some of the earliest electronic digital displays. Like most clocks that you plug into a wall outlet it keeps time by counting the frequency of the ac voltage 60hz. Its also a multiplexed design which means that only one tube is actually lit at a time but when you look at it you see all of the tubes lit.