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shield. The switch settings are shown in Table 240: Carrier Shield grounding switch settings on
page 557. The switch should be kept in UP (off) position.
Table 240: Carrier Shield grounding switch settings
Switch Down (On) Up (Off)
SW 4 – 1 Rx – FGND Rx – OPEN
SW 4 – 2 Tx – FGND Tx – OPEN
Receiver functions
The receiver extracts data and clock from an AMI (Alternate Mark Inversion) coded signal and
outputs clock and synchronized data. The receiver is sensitive to signals over the entire range
of cable lengths and requires no equalization. The clock and data recovery meets or exceeds
the jitter specifications of the CCITT recommendation G.823 and the jitter attenuation
requirements of the CCITT recommendation G.742. This provides jitter attenuation increasing
from 0 dB to 60 dB over the frequency range from about 6 Hz to 6 KHz.
Transmitter functions
The transmitter takes the binary (dual unipolar) data from the PCM transceiver and produces
bipolar pulses. This conforms to CCITT recommendation G.703 pulse shape.
Loopbacks
The remote loopback function causes the far-end device to transmit the same data that it
receives, using the jitter attenuated receive clock. The data is additionally available at the far-
end receive data outputs. Local loopback causes the transmit data and clock to appear at the
near-end clock and receive data outputs. This data is also transmitted on the line unless an
Alarm Indication Signal (AIS) is transmitted instead.
CEPT transceiver
The transmitter and receiver functions are used for synchronization, channel, and signal
extraction. The functions meet applicable specifications of the CCITT recommendation G.703
and G.732.
The transceiver provides transmit framing based on the 2.048 MHz clock derived from the
DS-30X system clock and 1 KHz framing pulse.
Architecture
Circuit Card Reference July 2011 557