Overview
This lecture explains T-carrier technologies, focusing on T1 and T3 lines, their historical use for voice and data transmission, and how newer broadband methods have largely replaced them.
Origins of T-carrier Technologies
- AT&T invented T-carrier technologies to transmit multiple phone calls over a single cable.
- Before T1, each phone call required a separate pair of copper wires.
- Transmission System 1 (T1) allowed up to 24 simultaneous phone calls on one twisted pair copper line.
T1 for Data Transmission
- Each T1 channel (originally for voice) can transmit 64 kbps of data.
- A single T1 line offers total data speeds of 1.544 Mbps.
- The term "T1" now refers to any twisted pair copper connection with 1.544 Mbps speed, regardless of strict adherence to the original standard.
T-carrier Adoption and Evolution
- Initially, T1 lines were used for connecting telecom company sites and other telecom companies.
- In the 1990s, businesses adopted T1 lines for faster internet access.
- T3 lines were developed by combining (multiplexing) 28 T1 lines into one, reaching 44.736 Mbps.
Modern Replacements
- T-carrier systems are still used but have largely been replaced by newer broadband technologies.
- Cable broadband and fiber connections are now preferred by small businesses due to lower costs.
- Fiber technologies have replaced copper-based T-carrier systems for internal ISP communication.
Key Terms & Definitions
- T-carrier — A family of digital transmission systems developed by AT&T to carry multiple signals over one line.
- T1 line — A twisted pair copper connection transmitting 24 channels at 64 kbps each, totaling 1.544 Mbps.
- T3 line — A high-capacity line formed by multiplexing 28 T1 lines, providing 44.736 Mbps.
Action Items / Next Steps
- Review the differences between T1, T3, and modern broadband technologies.
- Prepare to discuss reasons for transitions from copper to fiber in telecom.