The MicroVision is the very first handheld game console that used interchangeable cartridges. It was released by the Milton Bradley Company in November 1979. The MicroVision was designed by Jay Smith, the engineer who would later design the Vectrex gaming console. The MicroVisions combination of portability and a cartridge-based system led to moderate success, with Smith Engineering grossing $15 million in the first year of the systems release. However, very few cartridges, a small screen, and a lack of support from established home video game companies led to its demise in 1981. The processors for the first MicroVision cartridges were made with both Intel 8021 (cross licensed by Signetics) and Texas Instruments TMS1100 processors. Due to purchasing issues, Milton Bradley switched to using TMS1100 processors exclusively including reprogramming the games that were originally programmed for the 8021 processor. The TMS1100 was a more primitive device, but offered more memory and lower power consumption than the 8021. First-revision MicroVisions needed two batteries due to the 8021s higher power consumption, but later units (designed for the TMS1100) only had one active battery holder. Even though the battery compartment was designed to allow the two 9-volt batteries to be inserted with proper polarity of positive and negative terminals, when a battery was forcefully improperly oriented, while the other battery was properly oriented, the two batteries would be shorted and they would overheat. The solution was to remove terminals for one of the batteries to prevent this hazard. Due to the high cost of changing production molds, Milton Bradley did not eliminate the second battery compartment, but instead removed its terminals and called it the spare battery holder. MicroVision units and cartridges are now somewhat rare. Those that are still in existence are susceptible to three main problems: "screen rot," ESD damage, and keypad destruction.