Feature interaction 7-33
Digital Switching Systems DMS-250 ISDN Reference Manual MWC14 (CSP14)
DDD/IDDD calls
The NCS returns the routing response with action code set to originating
direct distance dialing/international direct distance dialing (ODI) offnet
parameters. The response contains a subsequent address and partition
number that is translated using standard DMS-250 switch translations. The
partition number is translated to an STS using table PARTRAN4. If the NCS
does not respond, an attempt is made to translate the called number in the
setup message using the STS from table CALLATTR.
For more information about calling number delivery and call type delivery
for VNET calls on a PRI, refer to “Identifying call origin—calling number
delivery” and “Identifying call type” in this chapter.
SAC service
A service access code (SAC) is a three-digit code using the same format as
an area code. SAC codes differ from DDD calls because there is no
geographical link between the number dialed and the terminator’s actual
geographic location. SAC codes are reserved for and allocated to provide
callers with access to a service instead of access to a specific geographical
area. The geographical link is not made until the dialed number is translated
into the actual routing information.
These nongeographic codes are reserved for and allocated to provide caller
access to interexchange or local exchange carriers (LEC). The first three
digits replace the numbering plan area (NPA) and designate a particular type
of switched service. The caller must always dial the access code in
connection with their respective services.
SAC is a basic service offering of the DMS-250 switch. No special
hardware, such as peripherals, circuits, or software loads are required for
domestic service. Hardware required for remote translations is dependent
upon the network platform used.
800 and 900 service
The DMS-250 switch receives 800 and 900 service calls over FGC and FGD
trunks. The 800 or 900 services calls are routed to the terminating switch
along with the ten-digit ANI (if received at the originating switch). If the
terminating trunk in the terminating switch indicates ISDN PRI, the
DMS-250 switch sends a SETUP message with optional ANI. The NSF
information element is set to 800 or 900 on the terminating PRI interface.
Call authorization
Call authorization on the DMS-250 switch occurs with authcodes, filed
hotline numbers, security codes, supplementary or account codes, and
calling line identifiers.
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