Voice Modems

7 hours ago

The Hayes Smartmodem introduced in 1981 established a key architecture where modems connected to computers via an RS-232 serial link, switching between control messages and data, a design still influencing modern cellular modems.
Voice modems emerged in the early 1990s, spearheaded by Rockwell, which introduced proprietary AT# commands for voice support, enabling PCs to handle phone calls, voicemail, and IVR systems by sending PCM audio over serial connections.
Voice modem usage was standardized in 1998 with V.253, but compatibility and implementation issues persisted, leading to limited consumer adoption largely focused on answering machine features despite broader business applications.
In modern systems, cellular modems retain the Smartmodem legacy by acting as standalone devices controlled via serial interfaces, with voice audio often transmitted digitally over separate UART channels, reflecting the persistent separation of call audio from the main OS.

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