Hayes AT command set

The Hayes AT command set, created by Dale Heatherington and Dennis Hayes for the 1981 Smartmodem, defines short text strings for dialing, hanging up, and adjusting connection parameters, initially supporting 300 bit/s modems. As higher-speed modems emerged, vendors added prefixed extensions (e.g., &, \) that were later standardized on Hayes extensions after the SupraFAXModem 14400 consolidated the market.