The mechanism of photoinhibition in higher plants and green algae

A rotatable transparent drum has a plurality of messages spaced therearound representing events which may occur at various remote points in a vehicle. An event sensor, a cam carried on an end surface of the drum, and a switch having a normally closed contact, a normally open contact, and a contact movable by the cam from engagement with the normally closed contact to engagement with the normally open contact are associated with a respective event and cooperate to control a drum drive motor and a lamp in response to the occurrence of the event to rotate the drum to position the message representing that event at a viewing window and to energize the lamp when that message is so positioned. An auxiliary cam and a switch having a normally closed contact and a contact movable out of engagement with the normally closed contact by the auxiliary cam cooperate with the vehicle starting switch and the drum drive motor to rotate the drum to a neutral position when the starting switch is positioned to start the vehicle engine.