T1 technology stemmed out of telephone lines, comprised of multiple copper and/or fiber lines twisted together in one cable. They were first made by AT&T in 1957 and first implemented in 1962 with the ability to carry 24 voice transmissions at once. T1 lines are basically many telephone wires twisted together in one, heavy, well insulated cable. T1 technology allows for digital transmissions while telephone technology is limited to analog. T1 lines are buried, dedicated lines capable of transmitting data up to 1.54 mbps, and are know to be very stable in severe weather.
Most businesses have to decide between Ethernet and T1 lines, and the decision includes cost, speed, stability and security. The cost of a T1 service is about 4 times the cost of an Ethernet service. The speed of a T1 line is at least 4 times the speed of an Ethernet line. However, an Ethernet line is not buried, and can be replaced and upgraded as new technologies demand. Burying the heavy T1 cable network makes them less susceptible to storms, and they have hubs inside of buildings instead of street corners, so accidents occur less frequently. Ethernet lines were built originally for residential use, and only packet technologies have allowed them to expand into the business realm. T1 lines were designed to be dedicated and secure without external technologies. However T1 can still be made faster and more secure as technologies allow.
When deciding between Ethernet or T1, a business needs to address it's own needs. A business that just wants to maintain a Website and have Email capabilities can save a lot of money using Ethernet Service Providers. Ethernet can stall on a daily basis, so a business needs to consider the urgency of Website updates as well as time sensitive emails. Phone (voice) calls can be made on traditional telephone lines. If a business requires a constant online presence, has a Call Center, or has sensitive data transmissions within or between networks, a T1 line is usually necessary.