7- 8 ADMINISTRATION OPTIONS AND REQUIREMENTS — SYSTEM 85

Field 5

Field 6

Field 7

V1-V2

For DS1, 0 is the only choice.

V 3 - V 4

This field is reserved for further use and contains a dash (-).

V1-V4

Used for assigning the framing format. The choices are D4 and ESF (previously referred to as Fe).

The choice of framing format is totally dependent on the equipment connected to the interface (such as D4-channel bank, channel-division multiplexer or CDM, channel-expansion multiplexer or CEM, host computer, and other switches). Normally the format is not dependent on facilities used, but older digital radio equipment may still be in place that only supports D4. The extended superframe (ESF) format consists of a better framing algorithm and therefore provides more reliable error detection than D4. ESF is preferred to T1 spans from System 75-to- System 75, System 75-to-Generic 1, System 75-to-Generic 2, System 75-to- System 85, System 85-to-System 85, System 85-to-Generic 1, and System 85-to- Generic 2. The D4 format should be selected for T1-spans connecting D4-channel banks and CDMs since they do not typically support ESF.

V1-V4

Selects per-channel signaling or common-channel signaling. This option deals with the way signaling bits are constructed for each DS0 channel. The default option is per-channel signaling (0).

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AT&T DS1/DMi/ISDN-PRI manual Field, V1-V2