PairGain 150-1236-54, Руководство пользователя

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Section 150-319-254
Revision 02
Page 4
copper pairs. Each of the two HDSL channels
contain 16 G.703 timeslots3.05 The transceiver
processes the HDSL
channels it receives and
passes them on to the ELU-319 multiplexer. The
multiplexer removes data link messages from the
HDSL channels and passes them to the
microprocessor. This enables the ELU-319 and the
ERU-412 Remote Unit to exchange operations
messages and status. By synchronizing to the FSW
of each channel, the multiplexer can reconstruct the
original 2.048 Mbps G.703 stream from the payloads
of the two HDSL channels. The CRC fields on the
HDSL streams enable the ELU-319 to determine if
errors are present on the channel due to excessive
impairments caused by impulse or crosstalk noise.
3.06 The reconstructed HDSL data channel is
buffered in a first-in-first-out (FIFO) buffer
within the multiplexer. A frequency synthesizer in
conjunction with the buffer regulates the output bit
rate and reconstructs the G.703 clock at the exact
rate received from the remote end. The HiGain
system operates at G.703 rates of 2.048 Mbps with
up to ±50 ppm of offset.
3.07 A G.703 interface driver converts the G.703
channel to a High Density Bipolar 3 (HDB3)
format.
3.08 The transmit and receive G.703 ports have
splitting access and bridging “Bantam”-type
jacks. Connecting one cable between the two BDG
jacks and another between the two LINE jacks splits
the XMT and RCV, creating metallic loopbacks
towards the customer equipment and HDSL line.
3.09 The ELU-319 contains two separate power
converters. The main power supply
converts -48V local battery to logic power for the
ELU-319 circuits. The line power supply converts
the -48V battery to either -130V for non-doubler
applications or -200V for doubler applications there
provides simplex power feed on the HDSL loops.
The line power can be turned on or off by the
microprocessor and automatically shuts down in the
presence of line short-circuits or microprocessor
failure.
Figure 2. ELU-319 Block Diagram. PairGain’s HDSL technology provides full-duplex services at 2.048 Mbps over copper
wires between an ELU-319 and an ERU-412 or EDU-451.