How are letters and parcels collected before they are sorted?

Before mail can be sorted, it must be collected from various sources, such as branch post offices and street mailboxes, and then prepared for processing. Because this collected mail contains a mix of standard letters, small parcels, newspapers, and magazines, it must first be segregated.1

Items that cannot be handled by machinery designed for standard letters—due to their size or shape—are separated from the "machinable" mail. This is often achieved using a segregator, such as a laterally inclined rotating drum, which receives a regulated flow of mixed mail. Mechanical devices on the conveyor belt then pick out letters that are of an excessive length or breadth, while the remaining standard-sized letters are delivered to the storage stacks of the facer-canceler equipment.1

Throughout this collection and preparation phase, postal systems utilize various materials-handling equipment, including mobile belt conveyors, roller conveyors, and forklift trucks, to manage the movement of mail sacks, containers, and loose parcels. These processes ensure that individual items are converted as rapidly as possible into a form that can be handled on a bulk basis.23