Chapter 1. System Overview and Modes of Operation
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MODES OF OPERATION
There are four modes of operation available with a D/I Mux III system. The three main modes of
operation are single channel bank, drop-and-insert, and dual channel bank. These modes relate to the
setup, timing, and structure of the T1 network. The fourth mode, Automatic Loop Protection Switching
(ALPS), is described in Coastcom’s ALPS User's Manual.
Channel Bank Operation
In channel bank mode, a D/I Mux III terminates a single T1 transmission line on its T1-1 port, as depicted
in Figure 1-17. The D/I Mux III can synchronize with the T1 network (loop timing mode), or supply timing
to the T1 network (local timing mode).
Figure 1-15. Channel Bank Operation
Loop Timing
System loop timing is provided by the clock recovered from the incoming T1-1 signal. If the
incoming T1 reference clock fails, timing is derived from the D/I Mux III's local timing source.
Local Timing
Local timing clock source for the T1-1 output is derived from the system's internal 1.544 MHz
oscillator. This oscillator can run freely, or be synchronized to one of three different clock
sources as follows.
• DB-9 Clock - The DB-9 clock is an 8 Kbps to 1.544 Mbps external clock (provided by another
system), brought into the Sync I/O connector on the back of the D/I Mux III shelf. The DB-9
clock is either a V.35/RS-422 differential Signal, or a Transistor Transistor Logic (TTL) signal.
• Slot 2 Synchronization Clock - The Slot 2 Sync clock is an 8 Kbps to 1.544 Mbps clock
recovered from a line card in slot 2 of the D/I Mux III shelf.
• Recovered T1-2 (Rcvd T1-2) Clock - The Rcvd T1-2 clock is the clock recovered from a T1
input signal connected to the T1-2 port.
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