Adapter for asynchronous devices

In combination with a document feeder for selectively feeding documents to an insert path of an insertion machine, a synchronizing circuit for synchronizing the feeding of documents by said document feeder to said insert path of said insertion machine;

• said insertion machine being operative in accordance with a predetermined machine cycle and having a vacuum line and being adapted to establish a given vacuum level throughout said vacuum line;
• first and second switches each having an open state and a closed state;
• said first switch being operative to close in response to a given level of vacuum in said vacuum line;
• a rotary magnet driven by said insertion machine in accordance with the machine cycle thereof and being rotated into and out of proximity to said second switch;
• and,
• said second switch being in series with said first switch and said document feeder and being operative to close and be held closed by a predetermined proximity of said magnet to said second switch whereby said document feeder is operative only upon the occurrence of both said given level of vacuum in said vacuum line and said predetermined proximity of said rotary magnet to said second switch.