Coastcom D/I Mux III System, User Manual

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Chapter 1. System Overview and Modes of Operation
9
Timing and Clock Source
Transmit clocks for the T1-1 and T1-2 transmission ports are derived from the sources illustrated in
Table 1-1 below.
Table 1-1. Clock and Timing Source
Clock Source Timing Source
T1-1/T1-2 Recovered Loop
Internal T1 Local
External Local
T1-2 Local
Slot-2 Local
With loop timing, the D/I Mux III in channel bank operation is synchronized to the T1 network. Clocks
recovered from the T1 network are used to create the T1 transmit clocks.
In local timing, the clock source for the T1 outputs is derived from the D/I Mux III internal 1.544 MHz
(Stratum IV) oscillator. This oscillator can either run freely, or be synchronized to an external clock.
In the drop-and-insert or dual channel bank loop timing mode, the D/I Mux III recovers clock from T1-1,
and uses this to create the T1-2 transmit clock. The T1-2 recovered clock is used to create the T1-1
transmit clock.
Alarms and Monitoring
Alarm detection is provided for both the T1-1 and T1-2 transmission lines. Common Bell System alarms,
as follows, are supported:
•
Local alarm
•
Remote alarm
•
Carrier Group Alarm (CGA)
Audible, visual, and minor alarm contacts are provided. The audible and visual contacts indicate major
alarms. A major alarm indicates a service-affecting problem that requires maintenance action. Visual
contacts indicate a minor alarm, which is not service-affecting. However, it does require maintenance
action.
Alarms are indicated by front panel Light Emitting Diodes (LEDs), and are reported by the closing of
alarm relay contacts. Alarms are reported to both the CCU and AMCU.
Loss of frame synchronization, or loss of the receive signal, activates a local alarm. If the condition
persists for 2.5 seconds, the local terminal sends a yellow alarm to the remote end. The direction of
yellow alarm transmission is user-configurable to either T1-1, T1-2, or both.
If a local alarm exists for a user-defined period, or if a remote alarm is received, a Carrier Group Alarm
(CGA) is generated to initiate trunk processing in the D/I Mux III. Trunk processing “busies out”
(removes) circuits in an orderly fashion.