Siemens identifies its products with an MLFB - the German abbreviation for machine-readable product designation, what most people just call the order number. It looks like 6ES7 314-1AG14-0AB0. You don't need to memorize every position, but recognizing the prefix tells you immediately what family a part belongs to, which is the key to identifying and sourcing it.
The prefix tells you the product family
- 6ES7 - SIMATIC S7 PLCs (S7-300, S7-400, S7-1200, S7-1500) and their I/O.
- 6SL3 - SINAMICS drives / variable-frequency drives.
- 6SE7 - older MICROMASTER / earlier drive families.
- 6AV - SIMATIC HMI panels and operator displays.
- 6GK - SCALANCE and other industrial networking / communication products.
- 6EP - SITOP power supplies.
- 6ED - LOGO! logic modules.
- 3RT / 3RH - SIRIUS contactors and relays; 3RV - motor protection circuit breakers.
- 3SE / 3SU - switches, position switches and command devices.
How the rest is structured
After the prefix, the digits encode the specific type, ratings and variant - but the field positions are NOT the same across families. The layout of a 6ES7 PLC number is not the layout of a 6SL3 drive number, so never assume a position means the same thing across prefixes. The final block (for example -0AB0 or -1AA0) generally indicates a hardware revision or firmware/version state of an otherwise identical part.
A note on documentation
Siemens removed the public MLFB structure documentation some years ago, so much of the position-by-position detail online is community-derived. For anything you are about to buy, the reliable move is to confirm the full order number against the official Siemens SiePortal / Industry Mall, which also shows the current lifecycle status (active, discontinued, etc.).
Why the revision suffix matters when sourcing
Two units with the same base number but different end suffixes are usually interchangeable, but not always - firmware or hardware revisions can affect compatibility in a specific system. When you request a part, give the complete order number including the suffix so the replacement matches.
Send us the order number
Have a Siemens MLFB you need - including obsolete S7-300 modules, SINAMICS drives or SIRIUS components? Send us the full number and we'll identify it and respond within two business days, with price and lead time where we have them and a full quote once our suppliers confirm. We are an independent reseller and not an authorized Siemens distributor; the Siemens name is used here for identification only.