Hoffman model KP706 Transolar Radio (1959). This transistor radio featured an array of silicon solar cells on top of the case, allowing it to be powered either by sunlight or batteries. Hoffman Electronics made the photovoltaic cell a marketable device. Hoffman solar or photovoltaic cells were used on the United States first satellite, Vanguard 1, in 1958. Hoffman expanded solar cell applications to the Consumer Products Division.