Time Division Multiplexing
Also called: TDM, E1 port · Topic: Infrastructure: Transport, Communications and Energy · NCERT: Beyond NCERT
Meaning
Time Division Multiplexing (TDM) is an older telecom technology that lets many calls share one line. It gives each call its own fixed time slot, and the slots take turns very fast. A call keeps its slot even when nobody is speaking, so some capacity is wasted. An E1 port is a standard link built on TDM. It carries 2.048 Mbps (megabits per second). Operators used E1 ports to connect their networks so that their customers could call each other. TDM now matters for one reason: India's telecom regulator, TRAI, is moving operators off it and onto IP-based interconnection.
Example
TRAI's Port Charges (Third Amendment) Regulations, 2026 take effect on 1 January 2027. From then, the old port charges (last revised in 2012) apply only to E1 ports. IP ports get annual price ceilings of ₹5.6 lakh for 1 Gbps and ₹42.3 lakh for 10 Gbps. A 1 Gbps port is roughly 488 times the capacity of one E1 port. All new interconnections must be IP-based, and existing E1/TDM links must move to IP in phases within three years.
Don't confuse with
- IP-based interconnection: TDM reserves a fixed slot for each call. IP sends data in small packets and uses capacity only when there is something to send, so it is priced by bandwidth (Mbps or Gbps).
- E1 port: an E1 port is not the technology itself. It is one standard link of fixed size (2.048 Mbps) that runs on TDM.