If you are looking for a software-based IP-PBX for Windows, 3CX offers a highly-regarded product. The current release versions of Asterisk are 1.2.37, 1.4.36, 1.6.0.28, 1.6.1.20. 1.6.2.13, and Asterisk 1.8.0. The current beta is Asterisk 1.8 beta 5.
An exoskeleton (from Greek Î­Î¾Ï, Ã©xÅ outer and ÏÎºÎµÎ»ÎµÏÏÏ, skeletos skeleton) is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton (endoskeleton) of, for example, a human. In usage, some of the larger kinds of exoskeletons are known as shells.
In electronics, an opto-isolator, also called an optocoupler, photocoupler, or optical isolator, is a component that transfers electrical signals between two isolated circuits by using light. Opto-isolators prevent high voltages from affecting the system receiving the signal.