Multi-Tech Systems ISIHP-2U - Manual (Page 18)

18 MultiModemISI Hybrid Series, ISIHP-2S/2U/4S/4U/4SD
Hardware Installation
ISIHP-2U LED Indicators
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-2S/2U is turned on.
• Flashes until SPIDs are verified with the
central office switch; then remains lit without
flashing.
• Indicates data link layer status.
LINE 2
P D
D
LINE 1
P