Stratum-3 Clock LED Strategy

Last Updated : Jul 06, 2015 |
Note:

When looking in the Stratum-3 cabinet, A card is on the left and B card is on the right.

The normal LED scheme is not followed for this device. Green LEDs do not indicate maintenance activity. There are no yellow LEDs, and there are more than three LEDs per circuit pack.

Removal of a card in the Stratum-3 clock may cause alarms to be resolved and the query test to pass. However, the removed cards should still be replaced to restore the Stratum-3 clock to full service.

The Stratum-3 clock has the following components:

  • 2 Clock Input cards (CI)

    Provides the logic to select the DS1 reference or Clock Input card. The red FAIL LED on this card indicates a failure with the card or the DS1 reference connected to it.

  • 2 Stratum-3 Cards (ST3)

    Provides 24-hour holdover. The red FAIL LED on this card indicates a failure with the card. Replace the card.

  • 2 Timing Output Cards (TOC)

    Provides cable length compensation, multiple output ports, selection of the ST3, and CI outputs. This type of card has two red failure LEDs: one indicates a failure of the card, the other indicates a failure in one or more output ports. In either case, replace the card.

  • 1 PBX (Private Branch Exchange) Alarm Interface (PAI)

    Filters power supplied to the clock, provides fuse protection, and provides alarm indications based on inputs supplied by other cards. The six LEDs on this card provide indications for the six alarm or status conditions as follows:

    • Loss of DS1 reference A

    • Loss of DS1 reference B

    • Loss of one clock unit

    • Loss of both clock units

    • Loss of one power supply

    • Loss of both power supplies

The output of the CI and PAI cards go directly to the TN780 Tone-Clock circuit pack via two 25-pair amphenol terminated cables. Every card has red and green LEDs for providing status or alarm indications. The abbreviations used in the table are defined above except for SRC (source) and Phase Locked Loop (PLL).

Table 1: Stratum-3 Clock LED Indications of

Card

Name

Color

Indication

PAI

REF A

Red

Loss of input reference A or CI A failed

REF B

Red

Loss of input reference B or CI A failed

ST A

Red

Failed Stratum-3 clock A

ST B

Red

Failed Stratum-3 clock B

PWR A

Green

-48VDC A present

PWR B

Green

-48VDC B present

CI

FAIL

Red

Card failure

DS1

Green

DS1 source present

CC

Green

Composite clock source64 present

SRC ACTIVE

Green

Card is currently on-line

ST3

FAIL

Red

Card failure

LOCK

Red

PLL lost sync with reference or holdover mode

REF A

Red

Timing Reference from CI A

REF B

Red

Timing Reference from CI B

TOC

FAIL

Red

Card failure

PORT ALM

Red

Output port alarm (one or more)

ST

Green

Reference present from ST clock

INPUT

Green

Reference present from CI

500’

Green

500-foot phase advance

1000’

Green

1000-foot phase advance

64Composite Clock (CC) source refers to the protocol used to electrically transfer timing from the Stratum-3 clock to the switch. The Composite Clock source is not relevant to the system.