The LIN (Location Identification Identifier) conveyed with an emergency call is used by the PSAP (Public Safety Answering Point) to query the ALI (Automatic Location Identification) database for important related data, such as location and callback number.
The ALI database must be pre-populated
with the LINs and their associated data by the responsible operator in advance of any emergency call being dialled.
In case of change in the corporate domain (new/modified/deleted LINs and/or data), ALI data have to be updated manually. There is no automated
capability to populate the E911 ALI database with LIN records.
In Lotus Sametime Unified Telephony, LIN pools are assigned to IP subnets, representing E911 Emergency Resource Locations.
For each LIN the following parameters are to be specified:
Location Identification Number:
This is a string of digits with maximum length 20. A leading "+" sign is allowed. The LIN must be unique throughout the BG.
The Callback Number is used by the PSAP station to call back to the ERL in case the emergency call was interrupted. If the Use Default Callback Number flag is not set, the callback is propagated to the original caller.
The Callback number must be unique throughout the switch.
Default Callback Number:
If the Use Default Callback Number flag is not set, the Default Callback Number is only used as a fallback in case the original caller doen't answer the PSAP callback. The same Default Callback Number (e.g. an attendant position) can be used for different LINs and in different subnets.
Use Default Callback Number
If this flag is set, a PSAP callback to the LIN's Callback Number is immediately forwarded to the Default Callback Number.
The Location Information
and Callback Number
s are mandatory and have to be made available to the PSAP's ALI DB before an emergency call can be successfully established.
Lotus Sametime Unified Telephony supports 100.00 LINs per BG.
Delivery of the LIN (and other E911 parameters) to the appropriate PSAP is by way of the PSTN (Public Switched Telephone Network) gateway, using SIP or SIP-Q. The elements used for LIN transport in the private network are:
Clear text in the SIP body in case if SIP interface
GNF format in the From and AI headers when the interface used is SIP
This allows the Lotus Sametime Unified Telephony server to identify that the LIN is a public number with a nature of address (NOA) of International.
CornetNQ element in case if SIPQ interface
The PSTN interface utilized by the PSAP is traditionally an analog CAMA trunk, although some PSAPs now use an ISDN PRI interface. As CAMA and ISDN/PRI curcuits do not have the ability to transmit location information the LIN is sent to the PSTN in the Calling Party Number.
An administrable flag in the Emergency Calling Subnet
setup controls LIN substitution
, i.e. whether Lotus Sametime Unified Telephony sends LIN information as a separate information element in addition
to the calling party number, or as the calling party number digits to the appropriate PSAP. This option permits the support of scenarios where the PSAP requires the LIN without supporting an emergency call specific interface - for example, if PRI (Primary Rate Interface) is used instead of CAMA (Centralized Automatic Message Accounting).
Parent topic: Emergency Calling