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.
Electron (or Vacuum) Tubes. An electron tube (also known as a 'Vacuum tube', or a 'Valve' ) is a glass or metal enclosure in which electrons move through the vacuum or gas from one metal electrode to another. The vacuum tube is often used to amplify weak currents or act as a one-way valve (rectifier) for electric current. Before the 1947 invention of the transistor the electron tube was the basis of virtually all electronic devices. The simplest kind of electron tube is the diode, which was invented in 1904 by John A. Fleming.
Making the world better, one answer at a time. A vacuum breaker is a mechnical device used to avoid backflow or a negative pressure in a plumbing system. It typically consists of an air valve with a spring holding it closed. When the pressure within the system is positive, the valve remains closed. In a vacuum breaker the moving contact and fixed contact are sealed inside a vacuum chamber. Electrons cannot flow in a vacuum, therefore as soon as the moving contact s â¦ eperates from the fixed contact the arc meets an infinite resistance and is immediately extinguished.