Emergency Call Frequency

For the part (a) I am not sure, so any expert is welcome to confirm…

a) the MS will select any network available, from any operator, as long as there is a roaming agreement between them.

b) To force the MS to “select” any operator, remove the SIM card. Then the MS is in “emergency” mode. (this i know because i tried it 🙂 )

Jason,

Unfortunately, GSM is not magic… If there is no operator covering the spot where you are, you are in deep trouble ! MS can only use GSM/DCS frequencies, nothing else.
Only “Satellite phones” have a global worldwide coverage.

Looking at MS-BTS / BTS-MS. It should not happen with multiple networks (850/900/1800/1900MHz) providing in an area, but don’t forget to check whether “Access Class 10” is broadcast (BTS-MS = point-to-multipoint) as well.

PIX

For Phase 1 the standard
GSM0211
4. ACCESS CONTROL
As regards Emergency calls (i.e “Class” 10), see note 2.

Note 2: This means that MSs in class 0-9, or without a valid IMSI, are not allowed to make emergency call attempts if “emergency call class” is barred.

For Phase 2+ the standard reads:
GSM0211
4.4 Emergency Calls
An additional control bit known as “Access Class 10” is also signalled over the air interface to the MS. This indicates whether or not network access for Emergency Calls is allowed for MSs with access classes 0 to 9 or without an IMSI. For MSs with access classes 11 to 15, Emergency Calls are not allowed if both “Access class 10” and the relevant Access Class (11 to 15) are barred (GSM 04.08 [6] refers). Otherwise, Emergency Calls are allowed.

I am just pointing out that in some countries it may be Phase 1 systems might still operate, but where Phase 2+ is relevant it still doesn’t automatically follow that emergency calls will be allowed.

In fact even handset manufacturers may not be entirely sure what facilities a mobile network may provide. The Nokia 6303 syas this:

Emergency calls
Important: This device operates using radio signals,
wireless networks, landline networks, and user-programmed
functions. If your device supports voice calls over the internet
(internet calls), activate both the internet calls and the
cellular phone. The device will attempt to make emergency
calls over both the cellular networks and through your
internet call provider if both are activated. Connections in all
conditions cannot be guaranteed. You should never rely
solely on any wireless device for essential communications
like medical emergencies.

To make an emergency call:

1 If the device is not on, switch it on. Check for adequate
signal strength. Depending on your device, you may
also need to complete the following:

• Insert a SIM card if your device uses one.
• Remove certain call restrictions you have
activated in your device.
• Change your profile from offline or flight profile
mode to an active profile.

2 Press the end key as many times as needed to clear the
display and ready the device for calls.

3 Enter the official emergency number for your present
location. Emergency numbers vary by location.

4 Press the call key.
When making an emergency call, give all the necessary
information as accurately as possible. Your wireless device
may be the only means of communication at the scene of an
accident. Do not end the call until given permission to do so.

Thanks PIX 🙂

Just add some more info (not sure it will help):

In UK use 999 (Emergency Services) and use E-112 (EU Emergency Services code allocation). However dialling 911 (US Emergency Services number) on MS, calls routed UK operator when MS located in UK. Not tried 911 when no SIM in ME.

What frequency does the US use for emergency cell phone calls? Do they have a particular frequency range that differs from regular cell phone calls?