Why is a T1 used for voice communications?
The main advantage of T1 is cost savings over equivalent service on regular analog lines. In general the cost of most 24 channel T1s is about the same as 12 standard telephone lines. This enables a business requiring 24 phone lines to do so for the cost of 12. Another advantage is that T1 is a digital transmission and therefore less prone than regular phone lines to loss and interference.