User guide

16
Chapter 2 - Hardware Installation
LINE 2
P
D
D
LINE 1
P
P LED Indicator
 Indicates U interface status connection.
 Controlled by NT-1, which converts S/T
interface (4-wire ISDN) to U interface
(2-wire ISDN).
 When U interface and S/T interface are NOT
active, LED remains off.
 Flashes 8 times/second (8 Hz)U interface
is attempting to activate.
 Flashes once/second (1 Hz)U interface is
active; S/T interface is not fully active.
 Lit, not flashingBoth U and S/T interfaces
are active.
D LED Indicator
 Lights when the ISIHP-2U is turned on.
 Flashes until SPIDs are verified with the
central office switch; then remains lit without
flashing.
 Indicates data link layer status.
ISIHP-2U LED Indicators
Figure 2-4. ISIHP-2U LEDs