Call Transfer

A Call Transfer is a telecommunications mechanism that enables a user to relocate an existing telephone call to another phone or URL, using a transfer button and dialing the required location.

Fax Voip Softphone supports 2 different methods for implementing Call Transfer – standard method and Hairpin Call Transfer (2 call legs).

Standard Implementation (recommended)

When a call transfer occurs, a control message (SIP REFER, H.450.2) is sent back to the other party to request that the other party initiates a follow-on call from the other party to the final transfer-to destination. The original call is usually not torn down until the "replaces" operation is completed successfully. The term replaces is used here in the context of "Call 2 replaces call 1”. If for any reason the replacement operation fails, the other party usually does not disconnect the call to the transferor. In some cases, the call replacement mechanism is not fully supported and only blind call transfer is possible. The standard transfer method results in an optimal direct call path between the transferee and the transfer-to party after the call transfer is committed.

The standard mechanism for Call Transfer usually supported by VOIP PBX in local network. Nevertheless, these mechanism often does not work in public VOIP networks for different reasons. We recommend to use standard mechanism where possible.

Hairpin Call Transfer (transfer-by-jone mode, 2 call legs)

This is an internal mechanism. In this case, the original transferee-to-transferor VOIP call leg is kept, and a second transferor to transfer-to VoIP call leg is created for the consultation call phase of the transfer. When the transfer is committed, the original and consultation call legs are simply bridged together. This method has the advantage that it has no end-to-end dependency on the capabilities of the transferee or transfer-to VOIP endpoint.

In this case the second transferor to transfer-to VoIP call leg is created based on Outgoing VOIP Call Routing rules – the same rules that you use for standard outgouing calls.The transferee can listen to music while waiting on the phone.

The Hairpin Call Transfer have no dependency on the capabilities of your VOIP network. Using these method you even can transfer SIP calls to H.323 and vice versa.