There is a switch on my game genie, what is it for?

my game genie, for SNES, has a switch on the front of it. when i push it up, or down, nothing happens. If its up while attached to the SNES (power on), the light next to the switch turns on (green). if the switch is down and attached to the SNES (power on), the light does not turn on. what is the purpose for this switch?