AT&T MERLIN LEGEND Release 2.0 Equipment And Operations Manual page 132

Hardware Components
An UPAM is needed because 48-VDC alerting devices require four contact
closures and the ground-start or loop-start ports only have two. The UPAM
provides the additional two.
Alarm
Trouble
A ground-start or loop-start power failure transfer (PFT) port can be used to
activate an alarm by connecting the port to an UPAM (see Figure 2-23). When
system trouble (software or hardware malfunction) is detected by the system
operator console, a signal is sent to that port. The port's switching contacts
close and send the signal on to the UPAM. The UPAM activates an external
alert.
Power Failure Alarm
A ground-start or loop-start PFT port can be used to activate an alerting device
during a power failure by connecting the port to an UPAM (see Figure 2-24).
When a power failure occurs, the switching contacts on the PFT port close and
send a signal to the UPAM, which activates an external alert.
NOTE:
A PFT telephone cannot be used on this port when the port is connected for
a power failure alarm.
Failure
Power DID Busy-Out
The PFT port on a ground-start or loop-start module can be programmed to
automatically short the "busy-out" wire pair associated with a group of DID
trunks. Normally a loop-start line/trunk is used as the busy-out pair. When a
power failure occurs, shorting this busy-out pair signals the telephone
company's CO that the DID trunks are out of service. Figure 2-25 shows this
connection.
NOTE:
Before the ground-start or loop-start module containing the PFT port for the
DID busy-out is removed, the busy-out pair must be shorted and then the
modular cord must be disconnected from the PFT jack. Otherwise, a false
busy-out will occur. The short is removed after the system is powered up.
2-58 Power-Related Hardware