The USPS uses 5 primary different pieces of equipment to sort mail.
- Advanced Facer-Cancelers
- These orient mail in the appropriate direction, apply postmarks and separate mail that can be dealt with by other equipment to the appropriate other equipment.
- Multiline Optical Character Readers
- These read machine-printed addresses on letter mail and print a POSTNET barcode in the lower right-hand corner, as well as performing an initial sort. The OCR equipment they use is actually fairly sophisticated, and definitely very fast.
- Mail Processing Barcode Sorters
- These read POSTNET barcodes, first checking the lower right-hand corner and then in the address region. (And sort based on that.) These can handle something like 30,000 pieces of mail in an hour -- that's about the same rate that a WWII era machine gun could fire bullets.
- Remote Barcoding System
- The single most expensive piece of equipment for them to use. Basically, a human reads what the mail says and the equipment puts a POSTNET barcode on it.
- Delivery Barcode Sorters and Carrier Sequence Barcode Sorters
- these sort barcoded mail into the actual order the carrier takes in their route using a full 11-digit barcode (ZIP+4 code plus 2-digit delivery point)