isr.co.ro : glossary Hayes-compatible Said of modems that respond to the same command set defined by Hayes Corp. for its modems. Also called "AT-compatible" from the prefix used for many of the commands. Unfortunately, over the years, Hayes has been forced to add commands to the list as modem speed and features have increased, and some of the commands and status codes have also required changes. Modem manufacturers have also implemented the standard in different ways and added their own features. So increasingly, the setup portion of communications and Internet software takes Hayes compatibility as a general architectural minimum but gives you a lengthy list of individual modems to select from.