The alternative meaning is an obsolete type of single-stage nuclear bomb that uses thermonuclear fusion on a large scale to create fast neutrons that can cause fission in depleted uranium, but which is not a two-stage hydrogen bomb. This type of bomb was referred to by Edward Teller as "Alarm Clock", and by Andrei Sakharov as "Sloika" or "Layer Cake" (Teller and Sakharov developed the idea independently, as far as is known). The idea of boosting was originally developed between Fall 1947 and Fall 1949 at Los Alamos.