Systems and methods for a communications transfer between internet protocol multimedia services and push to talk services

A system, comprising:

• a first communication device configured to
• establish a first full-duplex call with a second communication device while engaged in a half-duplex call with at least one third communication device, and
• communicate a REFER request message to the second communication device as part of a full-duplex call transmission over a full-duplex call infrastructure, said REFER request message including contact information for redirecting the second communication device to a hybrid application server and token information that is to be subsequently used to patch the full-duplex call into the half-duplex call without modification thereof;
• said second communication device configured to perform operations to re-direct the full-duplex call to the hybrid application server in response to the REFER request message, said operations comprising
• terminating the first full-duplex call, and
• establishing a second full-duplex call with the hybrid application server by using an INVITE message including the token information contained in the REFER request message without modification;
• and
• said hybrid application server configured to patch the second full-duplex call into the half-duplex call using said token information contained in the INVITE message.

A hybrid application server, comprising:

• at least one electronic circuit configured to
• concurrently be engaged in a first full-duplex call with a first communication device and a half duplex call with a second communication device, where the first full-duplex call is established with the first communication device using an INVITE message including token information contained in a REFER request message without modification, said REFER request message previously communicated as part of a full-duplex call transmission over a full-duplex call infrastructure;
• and
• patch the first full-duplex call into the half-duplex call using token information contained in the INVITE message received from the first communication device during call transfer operations of an Explicit Communication Transfer supplementary service.