AT&T DS1/DMi/ISDN-PRI manual Network Specific Facility, Synchronization

NETWORK CONNECTIONS AND CONFIGURATIONS 2-15

Network Specific Facility

For outgoing calls from the customer-premises side, the 4E11 and 4E12 will accept a network specific facility (NSF) but do not require that one be present.

For call-by-call trunk groups, the 4ESS will check for a NSF and will reject the call if one is not present.

Synchronization

A 4ESS is always synchronized to the AT&T reference frequency. Therefore, for special-access applications, the System 85 or Generic 2 normally uses a 4ESS as the master-clock source. A particular ISDN-PRI facility may or may not be selected as the clock reference to the switch, depending on the use and reliability of other interfaces. The rules and considerations for selecting a synchronization source are detailed in chapter 5, Synchronization of Digital Facilities.

System 85 R2V4, Generic 1, or Generic 2 to a DACS

The DACS does not provide a DMI-MOS or ISDN-PRI and does not support those types of connections. However, D4, ESF, and RBS are supported.

System 85 or Generic 2 ISDN-PRI to a 5ESS

A 5ESS is most frequently used by a LEC. It provides digital CO services, both to subscribers and customer premises switches. For ISDN applications, a 5ESS must be equipped with 5e4.2 or later software.

A System 85 or Generic 2 ISDN-PRI connects to the extended digital subscriber line (EDSL) circuit pack in a 5ESS (only those configured with 5e4.2 Generic implement the network).

A 5ESS may or may not be synchronized to the AT&T reference frequency. A 5ESS has a lower stratum clock (higher accuracy) than a System 85 or Generic 2. Therefore, this issue should be verified for each specific configuration.