Lotus Sametime Unified Telephony supports a callback mechanism that allows return calls to be placed from a PSAP (Public Safety Answering Point) directly to the device which placed the emergency call in case the call was interrupted. This works no matter to which callback number the delivered LIN (Location Identification Number) is mapped in the ALI (Automatic Location Identification) database and even with lines that are not provisioned for DID (Direct Inward Dialling). For Return Call from PSAP a special ring tone and display is generated.
This direct callback is achieved in the following way: During emergency call processing Lotus Sametime Unified Telephony
- determines the appropriate entry in the Emergency Calling table and - therein - the first unused LIN from the assigned LIN-pool.
- saves the callers DN, IP address and port number and associates it with the LIN's configured Callback Number
A Callback Number has to be configured for every LIN in Lotus Sametime Unified Telephony. It must be a registered DID number and it must be identical to the Callback Number mapped to the LIN in the ALI database of the responsible PSAP.
The PSAP operator will not know the name of the emergency caller (except during conversation), only the location and Callback Number stored for the received LIN is displayed on the PSAP monitor.
When a call to this Callback Number
arrives via a gateway, Lotus Sametime Unified Telephony
- identifies this as an emergency callback
- retrieves the DN, IP address and port number of the original Emergency Call and forwards the callback accordingly
Although LINs will be marked as unused after a certain time, the assignment logic might break if the number of emergency callers exceeds the number of LINs in the corresponding pool, so from a subscriber's point of view it is desireable to have an individual LIN and Callback Number. The downside of this is:
- A Callback Number has to be a registered DID number. In some countries (e.g. USA) each DID number has an associated carrier fee/charge associated with it.
- The amount of provisioning that has to be done
- A Business Group's Emergency Calling table is limited to 6000 entries.
If many users reside at the same location (from a PSAP's perspective) and this location can be identified by an IP address mask M
(or location domain D
), then associating M
) with a LIN pool in an Emergency Calling table entry, will greatly simplify provisioning, reduce the size of the Emergency Calling table and, ultimately, reduce costs.
Default Callback Numbers
For every LIN the administrator should configure a Default Callback Number
to which the callback should be forwarded in case the original emergency caller cannot be reached.
By selecting the Use Default Callback
option during LIN configuration, the callback to the original subscriber is disabled for this LIN and the return call is immediately routed to the Default Callback Number
. E.g. small businesses located in one building, one floor, may prefer to have one LIN to represent all possible callers and emergency callbacks to be directed to the front security desk.
Before 188.8.131.52 of Lotus Sametime Unified Telephony, an Emergency Return Call was signalled as normal external calls towards its recipient.
Since 184.108.40.206, Lotus Sametime Unified Telephony signals Emergency Return calls and Emergency Intrusion calls distinctively, which results in an emergency alerting tone at the phone (if supported and provisioned).
The preferred Emergency Ringing behaviour can be specified as a system-wide setting.
Lotus Sametime Unified Telephony features preventing the return call to terminate on the subscriber (e.g. Lotus Sametime Unified Telephony-based Call Forwarding or Do not Disturb) are bypassed.
Features, which are not activated on the system but on the device (e.g. device-based Call Forwarding or Do Not Disturb) will NOT
be overridden by an emergency callback!
How to Configure Distinctive Ringing for Emergency Return CallsParent topic: Emergency Calling
Whether or not Emergency Return Calls shall be signalled distinctively, can be configured at the switch level.