Because RFL™ and Hubbell® have a policy of continuous product improvement, we reserve the right to change designs and specifications without notice.
2.3.3.1 T1 Line Receiver
The CM4 receives its T1 line input from the DACS module port 5 or 6. The T1 format can be either
ESF (Extended Superframe) or SF (D4 Superframe). (See Section 10 for more information on
formats.) The line code can be either B8ZS (Bipolar with 8 Zero Substitution) or AMI (Alternate Mark
Inversion).
Equipment and monitor test jacks on the front of the Common Module accept miniature bantam plugs.
Plugging a T1 transmission test set or the output of another multiplexer into the "T1 EQUIP IN" jack
breaks the connection to the incoming T1 line. The terminating impedance should be 100 ohms
(balanced). The "T1 MON IN" jack permits test access to the line input without breaking the T1 line
connection. Equipment connected to this jack should also provide a 100 ohm termination impedance.
The signal level at this point is approximately 20 dB below the input.
The test jacks handle the T1 signal originating or terminating at the module on which they are located.
In redundant applications, test equipment should be plugged into the jacks on the currently active CM4
module in order to access the external signal. The inactive CM4 module is looped onto itself, and
therefore, its test jacks permit access only to the transmitter/receiver of that module.
The line receiver accepts the input signal, recovers receive timing, and decodes the bipolar signal. A
jitter buffer follows, to smooth out the timing jitter usually present on an incoming signal.
2.3.3.2 T1 Line Driver
The T1 line output connection is made through the DACS module port 5 or 6. The “T1 EQUIP OUT”
and “T1 MON OUT” jacks function like the input test jacks described above. All equipment connected
to them should provide 100 ohms of termination. The “T1 EQUIP OUT” jack breaks the connection to
the T1 line output. The “T1 MON OUT” jack does not break the connection, but the signal level at this
jack is about 20 dB below the output level.
2.3.3.3 Demultiplexing Of The T1 Aggregate To Individual Channels
The decoded line receive signal feeds the demultiplexer circuitry where it achieves frame
synchronization. The mean time to lose frame in the presence of a high random bit error rate (10
-3
)
exceeds several hours.
Once frame synchronization is achieved, the demultiplexer develops the proper demultiplexer bus
signals and feeds them to all the channels cards plugged into the shelf. Bus signals include
demultiplexed channel data, demultiplexer synchronization status, and synchronization signals
necessary for proper decoding by the channel modules.
M-DACS-T1 RFL Electronics Inc.
October 16, 2012 2-29 (973) 334-3100
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