TN775B/C boards are used in maintenance and monitor power failure
signals in an EPN cabinet in R7si/r or later.
circuit packs also monitor the clock, monitor and control the
power supplies and battery charger, and monitor air flow and high
These circuit packs provide 2 serial links to communicate with
Expansion Interface (EI) circuit packs, and provide an RS-232
interface for connection to an administration terminal. Each circuit
pack contains a 3-position switch to control emergency power transfer.
The TN775C Definity maintenance circuit pack is used in maintenance
and monitors power failure signals the D-channel links