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 E1 Line Receiver
The CM4 receives its E1 line input from a Module Adapter in multiplexers with electrical E1
interfaces, or from an OIA (optical interface adapter) in multiplexers with fiber optic E1 interfaces.
(See Section 12 for more information on formats.) The line code can be either HDB3 (High Density
Bipolar of order 3) or AMI (Alternate Mark Inversion).
Equipment and monitor test jacks on the front of the Common Module accept miniature bantam plugs.
Plugging a E1 transmission test set or the output of another multiplexer into the "E1 EQUIP IN" jack
breaks the connection to the incoming E1 line. The terminating impedance should be 100 ohms
(balanced). The "E1 MON IN" jack permits test access to the line input without breaking the E1 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 E1 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 E1 Line Driver
The E1 line output connection is made through a Module Adapter in multiplexers with electrical E1
interfaces, or from the OIA in multiplexers with fiber optic interfaces. The “E1 EQUIP OUT” and “E1
MON OUT” jacks function like the input test jacks described above. All equipment connected to them
should provide 100 ohms of termination. The “E1 EQUIP OUT” jack breaks the connection to the E1
line output. The “E1 MON OUT” jack does not break the connection, but the signal level at this jack is
about 20 dB below the output level.
In redundant applications, the test equipment should be attached to the currently active CM4 module in
order to observe the output of the shelf.
2.3.3.3 Demultiplexing Of The E1 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.
IMUX 2000E1 RFL Electronics Inc.
April 1, 2007 2-12 (973) 334-3100
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