Software Modems¶

(sometimes also called WinModems)

What is a Software Modem¶

Traditional analog modems are based around hardware modulators/demodulators, typically some kind of DSP or VLSI chipset including some kind of internal processor / software. They are basically an embedded system with two external interfaces:

• the analog phone line interface
• a RS-232 serial line towards a terminal or computer

As desktop computers and laptops became more powerful around the turn of the century, various manufacturers started to implement software modems. Those modems only contained the analog line interface and an ADC/DAC. All the actual signal processing (equalizer, modulation, demodulation, coding/decoding, etc.) happened in software running on the main processor of the desktop/laptop computer (typically an x86 CPU).

The related proprietary software for the main CPU was typically specific to a given vendor/chipset, and was offered in most cases only for Windows type operating systems, hence also the name WinModem. There were some exceptions where binary-only software was also offered for Linux or other OSs.

Models of Software Modems¶

FIXME