Get On Board with. Compass Card. Compass Card is the smart card and smart choice for transit passes in the San Diego region. Compass Card is your ticket for the Bus, TROLLEY, COASTER, and SPRINTER.ompass Card. Compass Card is the smart card and smart choice for transit passes in the San Diego region. Compass Card is your ticket for the Bus, TROLLEY, COASTER, and SPRINTER.
Use of Vacuum Tube Diodes Gradually p-n junction semiconductor has come in the market and vacuum tubes got replaced by them. The most basic structure of vacuum tube is vacuum diode. Still today somewhere vacuum tubes are being used widely. These fields for application of the vacuum tubes are in Atomic Clocks; Audio Systems; Car Dashboards
Modern vacuum tubes, mostly miniature style. In electronics, a vacuum tube, an electron tube, or just a tube (North America), or valve (Britain and some other regions), is a device that controls electric current between electrodes in an evacuated container. Vacuum tubes mostly rely on thermionic emission of electrons from a hot filament or a cathode heated by the filament.