Found below info in the 3300 docs. Looks like it supports it, on embedded t1 modules, but not NSUs (find that surprising!!)
I am a bit confused by the note that both calls must be connected to the same CO!! What if the caller is at home, connected to another CO.. they dial the DID# of the business, call comes from their CO to the closest Co to the business, call comes in on a PRI channel, reception wants to transfer to an outside cell #, home # or LD #. Will this service work, to avoid tying up two B channels for the duration of the transferred call"
Will it work on calls transferred though an AA to outside #s"
How about calls to an extension that is fwded to an outside #?
Two B-Channel Transfer (NI-2 only)
Description
Two B-Channel Transfer (TBCT) allows a 3300 ICP set user to transfer an external call to another external destination and have the two external parties connected through the trunks at the Central Office (CO). Because the calls are connected at the CO instead of at the 3300 ICP, the incoming and outgoing trunks on the 3300 ICP that would normally be required to connect the external parties are available for use.
TBCT is only supported for Bellcore and 5ESS variants of the NI-2 protocol for the embedded ISDN offerings of the 3300 ICP. It is not supported on the NSU.
TBCT Transfer
SMDR Recording
The 3300 ICP supports the tagging of TBCT calls by the CO. You can enable SMDR to record these tags and then use the tags to track the costs of TBCT calls. When the user initiates the transfer and the system releases the trunks, the CO sends the 3300 ICP a unique tag. SMDR appends this tag to the call record of the incoming trunk call. After the external call clears down, the CO then sends the same tag again to the system. SMDR then generates another record with this tag to identify when the external call cleared down. See SMDR Examples.
Note: Calls are charged as if the transfer had not taken place.
If the two ISDN trunks are located on the same system, the SMDR records for both of the ISDN trunks will contain the tag. In the case of a network transfer, the ISDN trunks are located on different systems and the systems are connected via DPNSS or IP trunks. In this case, the tag is written into the SMDR records of both trunks (ISDN and DPNSS or IP trunk) on the system that hosts the ISDN trunk that was on hold at the time that the transfer was initiated.
Network TBCT Transfer
Conditions
You must purchase support for TBCT from the CO.
TBCT must be enabled at the CO. If the feature is not enabled, a TBCT request from the 3300 ICP is ignored and the trunks are connected together through the 3300 ICP.
TBCT only works on trunks that are in the same Central Office PRI group. It does not work between Central Offices.
TBCT functions on a local 3300 ICP or across a private MSDN/DPNSS network.
Currently, the maximum number of active transfers supported by the CO is 127. If the maximum number of active transfers is already in use, a TBCT request from the 3300 ICP is ignored and the trunks are connected together through the 3300 ICP.
Interconnect, Tenanting, and COS restrictions that currently prevent CO trunk calls from being transferred together also prevent TBCT calls.
Programming
Enable "Two B-Channel Transfer Allowed" in the Class of Service Assignment form of the device (attendant console or set).
To enable SMDR recording of TBCT calls, set the following options to "Yes" in the SMDR Options Assignment form:
SMDR Extended Reporting Level 2
Two B-Channel Transfer Recording
If TBCT is being performed in a network, also set the following options to "Yes":
Standard Call ID Format
Standardized Network OLI
Operation
A user can initiate a TBCT from any device that can transfer a trunk call or form a trunk-to-trunk conference.
