Problems with answering calls via TAPI

The Asterisk Manager Interface does not provide an "Answer" function. This is logical as far as the Asterisk talks to the telephones via the SIP protocol and the SIP protocol knows an "auto-answer" but no "answer".

Solution / possible solutions for answering calls via TAPI

• Solution 1: For specially supported devices (e.g. snom or yealink phones), the TAPI driver can send an HTTP "Answer" command directly to the phone.
  • More infos...
• Solution 2: Via SIP header "auto-answer"
  • This variant requires a specially adapted/patched Asterisk system.
  • These SIP phones only have to be specially configured for this, but do not require any special firmware.
  • More infos...
• Solution 3: Via special SIP NOTIFY event
  • This variant requires a specially adapted/patched Asterisk system.
  • And the SIP phones also require specially adapted firmware.
  • More infos...

Solution 1: Call answering for specially supported devices

For specially supported devices (e.g. snom or yealink phones), the TAPI driver can send an HTTP "Answer" command directly to the phone.

In the TAPI driver line configuration under [Parameters for TAPI-controlled call setup > Special devices] you can see which telephones are currently supported. If you are using one of the phones listed, please select it.
Warning: For technical reasons, some entries only affect "MakeCall" but not "Answer".

Solution 2: Call answering via SIP header "auto-answer"

The TAPI driver can send a special redirect command to the manager interface of the PBX to answer a call. The system must then send a new SIP INIVITE with an auto-answer header to the telephone.

• This variant requires a specially adapted/patched Asterisk system. The supplier/manufacturer of the PBX system would have to make this adjustment.
  • Example of the special redirect command:ami_answer_by_redirect_example.txt
  • If the PBX can process the special redirect command, you would also have to enable the function in the TAPI driver under: [Asterisk Server - Settings > Tab "TAPI Functions" > Answer via Special-Context-Self-Redirect].
• Another requirement is that the "auto-answer by call-info" function is activated in the SIP telephones.
  • The same notes on "Auto-Answer" apply here that are described under "Answer the Originate call automatically".

Solution 3: Call answering via a special SIP NOTIFY event

• This variant requires a specially adapted/patched Asterisk system.
• And the SIP phones also require specially adapted firmware.

Answering incoming calls via CTI/TAPI using a special SIP NOTIFY (non-standard)

Requirements:

1. This option requires special adjustments in the telephone system that the manufacturer of the system would have to make.
2. The SIP-SoftPhone or the SIP-telephone responds to special NOTIFY events with parameter "Event: CtiAnswer".
3. If requirements 1 and 2 are met, you can also activate the function in the TAPI driver at:
   • [Asterisk Line - Configuration > Parameters for TAPI-controlled call setup > Special device = Standard > Settings > CTI Answer via SIP NOTIFY].

Functionality: When the TAPI driver receives a lineAnswer command via TAPI, it sends a special Action "Redirect". The system would then have to generate a special NOTIFY event with the parameter "Event CtiAnswer". The SIP-SoftPhone or the SIP-telephone then answers the incoming call.

• Sample log file (ast-answer.log) from the TAPI driver
• Sample log file (sip-answer.log) from the CTI Client SoftPhone