Coastcom D/I Mux III System, User Manual

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Chapter 3. Installation
64
Timing Sync I/O
External synchronization can be achieved with a DB-9 female external Synchronous Input/Output (Sync
I/O) connector. With it, the D/I Mux III can be configured for master or slave clock timing. (Refer to
Figure 3-14.)
Figure 3-14. Sync I/O Connector (Female)
Use external timing to synchronize two systems or networks. With external synchronization, the D/I Mux
III is the master timing source for the T1 network. Connect the DB-9 Sync I/O connector to 8 kHz Sync
(Pin 7) and Digital Ground (Pin 2) to achieve external synchronization. The DB-9 external sync
connector provides an 8 kHz frame-aligned, TTL-compatible, output clock for timing between co-located
D/I Mux III shelves. (To connect to another D/I MUX III, connect pin 2 and pin 8 TTL 8 kHz input.)
The Sync I/O input function can synchronize the D/I Mux III to another timing source. The input to the
Sync I/O must be 8 kHz or greater, and a multiple of 1600 Hz, up to 1.544 MHz. The driving balanced or
TTL signal amplitude cannot exceed plus or minus 5 volts, ground-to-peak value. The D/I Mux III shelf
will not synchronize to a composite clock (i.e., a 64K/8K source). Table 3-4 lists the most commonly
used frequencies and their tolerances. The synthesized 1.544 MHz T1 clock must have an accuracy of
±
50 Hz to qualify as a Stratum IV clock source. Accordingly, the input clock must be within this range to
allow this degree of accuracy. To calculate the reference clock frequency tolerance, use the following
formula.
Frequency Tolerance = [Frequency x (3.24 x 10-5)]