was invariably generated by rectifying the flyback pulses from the scanning circuitry rather than directly from the mains supply (a practice that survived the transition to transistor circuits). Although this provided a greater degree of safety, the reason for the change was that the mains transformer had been eliminated from sets produced from the 1940s onwards. External links http://www.earlytelevision.org/damper.html Early Television Museum article on efficiency diodes Vacuum tubes