the conveyor will be shut down relays and phototransistors along the conveyor collect information comparison circuits count the numbers of sheets reaching trays although some of these patents disclose limited aspects of microprocessor control none discloses the intercommunication and cooperation with a sophisticated computer controlled photocopier much of the utility of this invention relates to its flexibility in responding to tasks ordered by the photocopier its ability to store functions for later use to detect errors and to converse with its overlord photocopier makes this invention a valuable and much desired improvement over other machines a novel feature of this invention relates to a sophisticated collator 39 s ability to intercommunicate with and to respond to a computer controlled photocopier a logic control means on the collator of this invention has a programmable computer with a stored program unlike electromechanical relays or random logic control this computer is readily adaptable through reprogramming its function is not necessarily fixed although during any particular collator operation its function is predetermined the logic control means converses with the photocopier to receive job commands and information on the running of a particular job in the photocopier it acts upon these job commands to sort sheets principally in three modes proof stack or collate to aid its completion of a job the logic control means receives and processes signals from several sensors around the collator thus the job is completed more efficiently or notification as to a particular problem is.