BARS SPN/NXX/NPA

Commercial (off-net) calling using BARS (Basic Automatic Route Selection)...

BARS Network Translations:

A subscriber dials the BARS access code (AC1, usually '9'), followed by a number.
BARS tries to match the dialed digits in one of the following Translation Tables:

• SPN: If a caller dials a sequence of digits that matches an SPN, the switch waits until dialing is finished, then places the call. End of dialing (EOD) is assumed when the Network Interdigit Timer (NIT) expires after no further digits. The caller can bypass this delay by pressing "#" after dialing the number. The drawback to configuring in-country prefixes as SPNs is that the caller has to wait for the NIT/EOD timer to expire.
• NXX: If the first three digits dialed matches a NXX, the switch waits for exactly 4 digits, then immediately places the call. Until it sees 4 more digits, no call will be placed. Any digits dialed beyond the 4 are ignored. NXXs are useful for 3-digit prefixes to local telephone numbers. Countries that use seven digit numbers that include a three digit prefix, should be configured as NXXs.
• NPA: If the first three digits dialed matches a NPA, the switch waits for exactly 7 digits, then immediately places the call. Until it sees 7 more digits, no call will be placed. Any digits dialed beyond the 7 are ignored. If a country used area codes like the U.S., NPAs would be appropriate. Outside of North America there is little or no use for NPAs.

BARS Calling Sequence:

1. 9-xxx-xxxx... is dialed (9 is the BARS access code: LD 86 ESN, AC1=9).
2. In the Translation Table, digits dialed after “9” are matched to a SPN, NXX or NPA (LD 90 NET). The call is processed using the Route List Index (RLI) of the prefix (LD 86 RLB, RLI, FRL). If there is an SDRR for the RLI, some digits dialed after the prefix are allowed or denied.
3. If there is an FSNI for the RLI entry, the digits dialed after the prefix are either allowed or denied. The RLI’s Facility Restriction Level (FRL) is then compared to the NCOS/FRL of the station. If the station’s FRL (LD 11& 87) is equal or greater than the RLI’s FRL, the call proceeds.
4. An idle trunk is seized in the RLI’s trunk route (LD 86 ROUT and LD 16 RDB).
5. Are any digits to be Inserted or Deleted for the RLI (LD 86 RLB and DGT)?
6. The Dialed Digits with any modification are sent out on the trunk.

What to print:

Source: Nortel Training Documentation.