Enhanced Origination Services (EOS) for Toll Free (TF) telephone calls
consists of uploading instructions to the SMS/800 National Database,
which instructions are subsequently downloaded by Signal Control Points
(SCPs) in the United States for the routing of TF telephone calls. When a
caller dials a TF number, a communication switching device queries the
SCP serving the caller's LATA and routes the call according to the EOS
instructions for that TF number. EOS instructions route the call to a
POTS number in the originating LATA using an intraLATA Carrier
Identification Code. The POTS number is connected to a private gateway,
which utilizes the Dialed Number Identification Service (DNIS) of the
POTS number to perform a translation function, which may replace the
received DNIS with the DNIS of the originally dialed TF number. The call
is routed over the private network using the private network owner's
database for routing instructions for the specific TF number. The call is
routed through a dedicated connection to a facilities-based carrier or
called party or through a switched connection to an egress SSP or local
CO.