Voice modems are used in Axxon PSIM to automatically send voice messages when specified events occur (for example, a detector generates an event, an operator gives a command, or recording to an archive begins).

Axxon PSIM is compatible with the voice modems that do not encode (compress) audio streams or support the following audio stream encoding standards:

• 4-bit Rockwell ADPCM 7200 Hz,
• 4-bit IMA ADPCM 4800 Hz,
• 4-bit IMA ADPCM 7200 Hz,
• 4-bit IMA ADPCM 8000 Hz,
• 8-bit unsigned linear PCM at 7200 Hz,
• 8-bit unsigned linear PCM at 8000 Hz,
• 4-bit Rockwell ADPCM 7200 Hz,
• 8 bit u-law (G.711) at 8000 Hz,
• 8 bit A-law (G.711) at 8000 Hz.