Trunks and Multiplexing

A trunk is a high-capacity communication channel that connects switching centers, forming the backbone of telecommunication networks. Trunks are designed to carry large volumes of voice and data traffic simultaneously over long distances using multiplexing techniques.

Unlike local loops that connect individual subscribers to the nearest switching office, trunks handle the bulk transmission of aggregated traffic between network nodes. They represent the core infrastructure that enables telecommunications networks to scale efficiently.

Features

The characteristic features of trunks are:

• Digital transmission − They carry digital information as opposed to analog signals used in local loops.

• High bandwidth − Designed to handle very high data rates for simultaneous transmission of thousands of calls.

• Long-distance capability − Optimized for carrying signals over hundreds or thousands of kilometers.

• Multiplexing support − Use time division multiplexing (TDM) and frequency division multiplexing (FDM) to combine multiple signals.

• Fiber optic technology − Modern trunks predominantly use bundled fiber optic cables to achieve maximum bandwidth and reliability.

Types of Trunks

• Toll Connecting Trunk − Connect end offices (local exchanges) with toll offices (long-distance switches). These use fiber optic cables and handle regional traffic aggregation.

• Intertoll Trunk − Very high bandwidth channels connecting toll offices across different regions. These use advanced fiber optic systems and microwave links for intercity and international communication.

Multiplexing in Trunks

Multiplexing is essential for trunk efficiency since installing many low-bandwidth channels costs nearly the same as fewer high-capacity channels. Two primary multiplexing techniques are used:

• Time Division Multiplexing (TDM) − Users share the full bandwidth by taking turns transmitting in assigned time slots. Common in digital trunk systems.

• Frequency Division Multiplexing (FDM) − Different signals are assigned separate frequency bands within the trunk's total bandwidth, allowing simultaneous transmission.

Conclusion

Trunks form the high-capacity backbone of telecommunication networks, using multiplexing techniques to efficiently carry thousands of simultaneous communications over long distances. Modern trunk systems rely primarily on fiber optic technology and digital multiplexing to achieve the bandwidth and reliability required for today's communication demands.