Asterisk voicemodem cards: link: "First, Digium's X100P never really was a Digium product. It is just a fax modem PCI card. Any fax modem PCI card with the Ambient MD3200 chipset on it will work with Asterisk and the Zaptel wcfxo driver. Digium just bought those in bulk and sold them as X100P. The modems are typically available for 8 USD or so. In other words, what you paid Digium for was mostly support. However, the MD3200 chipset is being phased out. Intel acquired Ambient a few years ago and replaced the MD3200 chipset with a newer smaller version called the Intel 537 chipset. In principle, fax modem PCI cards with the Intel 537 chipset could also be used with Asterisk, but this requires some adjustments in the Zaptel wcfxo driver."