CapiSuite is an ISDN telecommunication suite providing easy-to-use telecommunication functions which can be controlled from Python scripts. It uses a CAPI-compatible driver for accessing the ISDN-hardware, so you'll need a CAPI-compatible driver. CapiSuite is distributed with two example scripts for call incoming handling and fax sending. They provide a multi-user answering machine with fax recognition, remote inquiry, and fax receiving/sending functions.
Sipcat is a software IP telephony system that helps businesses increase productivity and reduce telecommunication costs. It allows you to start running your own voice over IP PBX in a matter of minutes. It contains a complete Linux distribution, including Asterisk and all required 3rd party software.