LoudHush is a softphone application for Mac OS X. You can use it to connect to the Asterisk PBX running in your office or to a VOIP provider that supports the IAX protocol. With LoudHush you can initiate and answer, hold and transfer voice calls using your computer.
LoudHush is written in Cocoa/Objective-C and integrates nicely within the OS X environment. Is is distributed as shareware software, so when running unregistered it has the same features as a registered copy, but it automatically quits five minutes after being started.
Download the archive (compatible with Mac OS X 10.5, 10.6):
LoudHush is no longer actively supported or maintained.