Shift lock and position indicating torsion spring activated key switch

A shift lock mechanism for photo-optical switch apparatus comprising,

• an insert member including means for snap-in insertion of said member in a respective aperture in a keyboard array of apertures,
• a slidable shutter member including an aperture therein, said shutter member being vertically, slidably movable in said insert member effective in one position to block light from a light generator to a light receptor and in another position to permit light to pass unobstructed from said light generator to said light receptor,
• said shutter member further including an external, horizontally disposed, biasing member for biasing said shutter member vertically upwardly into a light blocking position within said insert member,
• an externally supported demountable, removable cam member slidably horizontally received on said shutter member in diametric opposition to said horizontally disposed biasing member and including means for demountably, receiving and guiding a cam follower member therein, and
• a cam follower member loosely slidably mounted on said insert member with one end inserted in said insert member and axially aligned with said horizontally disposed biasing member, the opposite end of said follower member engaging said demountable cam member effective in one position to lock said shutter member in a light passing position and in another position to block the light from said light generating member.