50 Candlepower, 200 Watt, double cage, tantalum filament lamp.

The Siemens & Halske Company in Germany began experimenting with rare metals in 1901 and developed a tantalum filament lamp in 1902 which was available for sale in Europe by 1905. The company secured all the worldwide sources of this rare earth metal and retained manufacture of the filaments throughout its relatively short commercial life.

Tantalum filaments were the first to be produced by a drawn wire process, producing a more robust filament, compared to the carbon filament. The length of filament required to allow these lamps to run on ordinary mains voltage meant that they were much longer than the loop or spiral formations of earlier carbon filaments. This led to the 'squirrel cage' style of filament windings, supported on radial wires held on a central glass rod.

Physical Description

240 mm (9.5 inch) circumference glass globe. Straight tantalum filament, zig-zagged circumferentially between 12 wire supports in a double 'squirrel cage' arrangement. Exhausted at top of globe. Brass bayonet cap. Double pin contact.

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