How does the mail processing center sort and distribute mail and What is an LSM?

When you hastily drop a letter into a mailbox, you might pause to check the collection times posted on the box, but beyond that you may never contemplate the massive operation of sorting and distributing mail which goes on around the clock, and largely behind the scenes.

The mail is picked up and taken either to a local branch office, or straight to a processing center, of which there are four in New York City. Different fates await the various classes of mail, registered, special delivery, and so on, but a first class letter of standard size travels the following route.

The mail is dumped helter skelter onto a wide conveyor belt. En route to the first machine, an automatic culler removes oversized letters and packages that can’t go through the Mark II facer canceler.

This machine (which is about waist high and is overseen by one or several workers) does just what the name implies: it faces the letters in one direction to facilitate later handling, and it cancels the stamp.

The letters go in upside down, backward and forward. The machine sends those with stamps in the upper corners (or somewhere in the upper portion) through a canceler and into the first trays; those with stamps on the bottom corners are flipped by two overlapping rubber coils that rotate continuously. After being flipped, these letters shoot through a canceler and into other trays.

The canceler, which thus finds the stamp wherever it is, contains an ultraviolet light that picks up a phosphorescent dye in the stamps, so letters with fake stamps or none at all will be caught and separated for return. The letters whiz through at a rate of 20,000 per hour.

If an oversized or bent letter gets into the machine by mistake and jams it, the operator must retrieve it immediately or he’ll have a dozen rumpled letters backed up in an instant like a chain reaction highway accident. Should this occur, wrinkled letters and torn envelopes are handled manually during the remainder of the sorting process.

If all is running smoothly, neat stacks of canceled letters are collected by hand and taken to a huge letter sorting machine, usually referred to as an LSM. At the Morgan processing center in Manhattan, the largest such installation in the world, there are seventeen LSMs, each consisting of twelve consoles attached to a large wall with 277 different bins.

Two loaders place the letters upright in containers beside each console operator. A suction arm picks up one letter at a time and whisks it in front of the operator, who punches its zip code on two rows of keys on the console.

The arm puts a letter per second in front of the operator, who must in that time find the zip (which is often scrawled and nearly illegible), press the right keys, and get ready for the next letter. If the mail is local, the operator looks only at the last two digits of the code, which represent the local branch; but if it’s headed for California, he may have to punch the first three or all five, depending on the breakdown of areas.

The first three digits indicate the zone, of which there are nine in the United States, and an area sectional center. (Omission of the zip code automatically causes a delay in service, as these letters are routed to manual handlers.) The numerals that are punched direct each letter into a slot on a large conveyor belt, which takes it to the appropriate bin, along with other letters designated for the same area. Five workers stand by the wall of bins and empty each bin when it’s full into a cardboard tray, covered with a sleeve, to be sent to the proper destination.

First class mail travels by air, so if your letter is not going to a local address or nearby state to which surface delivery is most expedient, it will be taken by truck to an airport. John F. Kennedy, LaGuardia, and Newark airports are all equipped with postal facilities where mail is loaded onto the planes of whatever commercial airlines are available.

It’s possible that your letter could arrive at the airport only twelve hours after you mailed it, for the processing centers work continuously, handling 17 million pieces per day in New York City alone, with the greatest volume of mail at night. (The earlier you mail your letter the better, for the volume increases as the day goes on.) Most local mail can be delivered the following day; letters to nearby states (such as Pennsylvania, New Jersey, Connecticut, and Massachusetts) may take two days; service from New York to California generally takes three days.

In Los Angeles, a postal facility at the airport sends the boxes of mail to the appropriate area processing center. There the letters again run through an LSM to be sorted for a specific local branch. Local post offices receive mail at night, sort it manually by street and block, and place it in the case of the carrier for that area.

A letter carrier arrives early in the morning, picks up his batch of mail, sorts it by building, and makes his rounds. Once the nine numbered zip system introduced by the Postal Service in February 1981 is fully operative, sorters aided by new technology will be able to sort the mail by precise block and house. The centerpiece of this new technology is the advanced optical character reader (AOCR), which is being used now to a limited degree.

This extremely efficient, fully automatic machine faces, cancels stamps, and sorts, all at a rate of 40,000 pieces per hour. The only drawback is that the AOCRs can only handle envelopes of standard business size with typed or printed addresses and zips. Although useful for large mailings by corporations, they can’t cope with the glut of multisized envelopes at Christmas and Valentine’s Day. By 1986, however, when the new system will be fully deployed, half of the LSMs will have been replaced by optical character readers, which scan the zip code and pass the letter on to another machine that prints the code in bar form on the envelope.

This bar code, used on most grocery products, will facilitate handling by machine all the way down the line.