Emergency calls from XT phones possible when network is down
It is possible to make 111 emergency calls even when XT goes down, Telecom says, after media reports stating the opposite have surfaced.
The specifications for the Global System of Mobile Communications, or GSM, require that handsets can be used to make mobile calls even when they’re out of credit or locked. On some networks, emergency calls are possible without the SIM card inserted too, but in New Zealand, it has to be in the phone.
As long as there are other mobile networks within reach of the customer’s phone, dialling pre-programmed emergency numbers such as 111, 112, 999 or 911 forces the handset to make a call on any available network. For GSM handsets, 112 is the standard emergency call service number but in New Zealand, the 08 international emergency number also works.
However, at today's press briefing on the XT outage, Telecom CEO Paul Reynolds said some phones may not switch over to alternative networks when they lose voice coverage but still have SMS or data service. This appears to have been the case in last night's incident.
Reynolds says others reported the incident and there were no delays in response caused by XT issues.
To be able to see another GSM network, handsets have to support the frequency band it uses. Telecom’s XT 3G network uses 850MHz mostly, with 2100MHz in parts of the major cities. Vodafone’s 2G GSM network operates in the 900 and 1800MHz bands, and its 3G network in the 900MHz and 2100MHz ones.
Like Vodafone, 2 Degrees’ GSM network operates in the 900 and 1800MHz bands.
XT 3G handsets and GSM phones cannot roam onto Telecom’s old CDMA network, however.