Palmmicro designs and sells chips, reference designs, and software for VOIP devices (IP Phones and ATAs)
Many part of their software API is Open Source with GPL license.

Website: www.palmmicro.com

Chips

• PA1688/PA168 MCS8051 based VOIP Chip — discontinued but still in wide use and still supported for bug fixes
• AR1688 Z80 based VOIP Chip — replacement for PA1688

The PA1688 design was originally done by Centrality Communications
many of the people moved to Palmmicro when Centrality discontinued its VOIP business in 2006.

Resources

• Blog by one of the developers with lots of technical information and updates
• Support email: support@palmmicro.com
• AR1688 and PA1688 based IP phone mailing list — http://groups.yahoo.com/group/palmmicro

Companies using the AR1688 in their products

• Digitmat — www.digitmat.com
• High-link — www.high-link.cn
• Yuxin — www.yntx.com

Companies using the PA1688 in their products

• http://www.tclcomm.com/ TCL-IP(6)
• http://www.yntx.com/en/index.htm
• http://www.unisenonline.com.cn/index1.htm (IP8008)
• http://www.atcom.com.cn/
• http://www.vida21.com/
• http://www.maxlink.com.cn
• http://www.iplink.cn
• http://www.5111soft.com/en/index.html
• http://www.xinyitong.com
• http://www.qiaoxing.net/english/cosunproduct/DEFAULT1.asp
• http://www.high-link.cn