Hayescompatible

Hayescompatible is a term used in telecommunications and computer hardware to describe devices, interfaces, or software that implement the Hayes command set for controlling dial-up modems. The name honors Hayes Microcomputer Products, whose Smartmodem introduced the AT command family in the early 1980s and established a de facto standard for modem control.

Under the Hayes command set, a control string begins with the letters AT and is followed by letters and parameters that configure the modem, dial numbers, or control its behavior. A typical exchange starts with an AT to verify the device, followed by commands such as ATE0 to disable echo, ATI to identify, ATDT to dial, ATA to answer, and ATH to hang up. The modem responds with textual codes such as OK or ERROR.

Hayes-compatible devices range from original 300–2400 baud modems to today's USB or PCIe modems and software that emulate modem behavior. While the exact command set has evolved and many vendors add extensions, the basic AT command family remains widely supported, and many software libraries still expose Hayes-compatible interfaces for compatibility with legacy equipment.

Because the term signals legacy compatibility rather than a single standard today, Hayescompatible hardware or software is typically found in contexts dealing with embedded systems, industrial equipment, or retro computing, where reliable serial modem control is required.