AT&T DEFINITY 7100 series Manuel d'utilisateur télécharger pdf (Page 66)

CONTROL CIRCUIT PACKS

Terminates the fiber optic link(s) between the PPN cabinet and the

EPN cabinet.

Maintenance TN775 (G3sV2, G3vsV2, G3iV2)

The TN775B is used for system maintenance and performs the fol-

lowing functions:

●

Monitors power failure signals

Monitors the clock

Provides two serial links to communicate with expansion

interface circuit packs

Contains a three-position switch that controls emergency

power transfer

Monitors and controls power supplies and battery charger

Monitors air flow and high temperature sensors

Provides an EIA-232 interface for connection to an

●

administration terminal.

Maintenance/Test TN771D (G3V2)

The TN771C performs the following maintenance functions:

●

Packet bus reconfiguration, which allows diagnosis and

correction of recoverable packet bus failures before the

link-access procedure on the D-channel (LAPD) links,

which use the bus, fail. LAPD is a link-layer protocol on

the ISDN-BRI and ISDN-PRI data link layer (level 2).

LAPD provides data transfer between two devices, and

error and flow control on multiple logic links. It recovers

packet bus failures involving up to three malfunctioning

leads (one or two data or parity leads, and one control

lead) by swapping spare leads with malfunctioning leads.

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AT&T DEFINITY 7100 series Manuel d'utilisateur Page 66