Linux has as its roots the Unix operating system which was developed in the 1970's. It was used by telephone companies then and it's used the same way today as well. A significant advantage of Linux is its compact efficient architecture, fault resilience, and high reliability. Another significant benefit is its stability. If you're familiar with Unix and Linux, you know the benefit of an O/S which is evolutionary in nature yet continuously advances to take advantage of modern methods and technology as it arrives.
For telecommunications, Linux is the operating system of choice. DAC Systems IVR is based on Linux accordingly.