The Svetlana™ 4CX5000A/8170 is designed for audio and radio frequency applications. It is particularly well-suited for use in VHF FM broadcast transmitters in the Band II 88-108 MHz frequency range. The Svetlana 4CX5000A/ 8170 has a directly-heated thoriated tungsten mesh filament for mechanical ruggedness and good VHF electrical performance. This modern mesh filament design is superior to the old hairpin design of the 1950's. In some VHF applications, the input circuit may need minor tuning to use the Svetlana 4CX5000A/8170 as a replacement because of the low inductance of the Svetlana mesh filament. No adjustments are required in Audio, MF or HF equipment. The Svetlana 4CX5000A/8170 is manufactured in the Svetlana factory in St. Petersburg, Russia, and is