Mellotronists

A little question related to Mellotrons I guess, or to early 
experiments with samplers, who knows, just because I am 
always curious when I can't find good answers after searching 
the www. OK, has anyone informations what exactly a 
"PROJECTRON" is? It's been used (or at least credited) on the 
early albums of Alan Parsons Project - "which" has not used 
Mellotrons as far as I know. Who knows something more?

Thomas