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Some Emergency Service provider's phone systems do not send the Connect message to establish the call fully end to end, even after the operator answers the call. If the call originates from a SIP device or a Lync client it will result in one way audio. This Best Practice describes how to configure the Sonus

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1. From the WebUI, access the Monitor tab.
2. View the channels used for PSTN connection to the Emergency call route (for both Analog and Digital routes).
   
   1. If the channels show in Alerting state but the other side answered the call, the emergency call was not connected. See Step c.
   2. If the channels show in normal state, and the emergency call connected, no other configuration is required.
   3. Configure the SBC for Emergency Services.

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Verify through Logs

1. From the WebUI, access Logs. See Working with Logging.
2. Ensure the log level is set to Trace (see Managing Subsystems Logging).
   1. For CAS: Set to CAS TRACE level.
   2. For ISDN: Set to ISDN TRACE level.
3. View the logs. The connect message data (noted in the red lines below) should be present in the logs for 911 calls. These messages indicate the PSTN is sending the connect message to the SBC. If these lines are not present, you must configure the SBC for emergency services.
4. Configure the SBC for Emergency Services.

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1. Access Settings> Telephone Mappings Table.
2. Create and configure a Message Translation table (i.e., Alerting to Connect). See Creating and Modifying Entries to Message Translation Tables).
3. Configure Message Type as Alerting/180 Ringing.
4. Apply changes.

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For ISDN calls

1. Access Settings> Telephone Mappings Table.
2. Create and configure a Message Translation table (i.e. Proceeding to Connect). See Creating and Modifying Entries to Message Translation Tables.
3. Configure Message Type as Proceeding (ISDN only).
4. Apply changes.

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Step 2: Create Transformation Table

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1. Access Settings> Transformation.
2. Create a call Transformation Table for 911 calls (i.e., LyncToT1-911). See Creating and Modifying Entries to Transformation Tables.
3. Configure per parameters below.
4. Apply changes.

For all Other Call Destinations

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1. Access Settings> Transformation.
2. Create a call Transformation Table for all other call destinations except 911 (i.e., Lync to T1). See Creating and Modifying Entries to Transformation Tables).
3. Configure per parameters below.
4. Apply changes.

Step 3: Add Transformation Table to the Call Route Table

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1. Access Settings > Call Routing Table.
2. Create a Call Route for 911 calls (i.e., Emergency Calls).
3. Select the Number/Name Transformation Table that includes 911 specifications (i.e, LyncToT1-911 calls).
4. (For CAS only) Select the Message Translation table that includes Alerting/180 Ringing (i.e., Alerting To Connect).
5. (For ISDN calls only) Select the Message Translation table that includes Proceeding (ISDN only) (i.e., Proceeding To Connect).

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For all other IP calls

Add a Transformation table (LyncToT1) to the Routing table used for routing IP calls to the T1 carrier.

1. Access Settings > Call Routing Table.
2. Create a Call Route for all IP calls (not 911).
3. Select the Number/Name Transformation Table created for all IP calls (i.e, LyncToT1 calls).

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