question on E&M interface

[kayih]

I read on this forum that a E&M interface can handle only one call at a time. So why do we call it a Trunk, and so what's the point of using E&M instead of FXS if both can handle only one call.

cheers

[paolo bevilacqua]

You call it a trunk because the word trunk was used in telephony starting the year 1900 probably, to mean a circuit between two exchanges as opposed to a circuit between subscriber and exchange.

The points of using it instead of FXS/FXO are multiple:

- Separate TX and RX pairs for eliminate return echo.

- Ability to pass digits in both directions, FXS/FXO passes digits from FXO to FXS only

- Support for disconnect and answer supervision.

All very importan things.

Hope this helps, please rate post if it does!