echo cancellation
This function prevents unwanted echo effects that can occur when signals are sent and received at the same time, for example, in telephony
EHS port
DHSG is known as EHS (meaning: "Electronic Hook Switch") in English; this is an electronic interface for wireless headsets, which have speakers, a microphone and – for the EHS function – a call acceptance and termination button
exchange line routing
In an ICT system, this regulates the distribution of incoming external calls (incoming exchange line routing) and the handling of outgoing external calls (outgoing exchange line routing)
external line key
Direct assignment of an exchange line