Emergency calls (to 999 and 112) from a Chorus desk telephone send a special caller-ID telephone number, instead of the normal one. One such emergencies-only number is allocated to each building, selected based on the site-specific IP address allocated to the telephones. The emergency services have been told which emergency-only caller ID number corresponds to which building. This allows them to arrive at the correct place even if the call is cut off or the caller is incapacitated.
Therefore the Chorus network should not be trunked across the backbone or taken between separate buildings over fibre or copper connections: to do so would mean that telephones’ locations would be misreported, sending emergency crews to the wrong place.
It is the responsibility of the owner of each network to comply with this recommendation.
Calls to the emergency services made from a soft phone cannot have their location identified in this way: the IP address allocated to your laptop, smartphone, or other device may not even be University-managed, particularly when using Wi-Fi. These will still be sent to emergency services, but will be tagged with a DDI number associated to Security Services as we do not know where they are. The caller can provide location details direct to the emergency services -if they are unable to speak to the emergency services and emergency services ring back, they will be answered by Security Services who will have some knowledge of the call from the alarm report.
There have also been phone faults where DHCP packets have not been sent back to the correct phone due to the Chorus network being trunked to an annex.