This device was used as a timing source in old, relay based, railway signalling systems. The mercury oscillates in the U tube. There is a long contact and few shorter ones. Some are used to set the oscillator in motion, when the mercury breaks the contact it swings back, but others re used to provide various timing signals and flash lamps. Electrodes are at different lengths to provide different timing signals, but of course all in phase as they stem from the same source