CXR 54500-16, Руководство пользователя

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5−
43
The 54541/54542 SMC block diagram appears in Figure 5-8. Refer also to
Section 3, Specifications, paragraph 3.377 or 3.387, for a detailed description
of the measurements that this card performs.
5.1021 Input Select Switch and Input Select Switch Decoder
Under microprocessor control of the Input Select Switch Decoder (ISSD), the
input select switch selects two of the five inputs for measurement and
performance monitoring. The choices are primary, secondary, and one of
three external inputs.
5.1022 Dual DS1/E1 Receiver, Clock Adapter
The dual DS1/E1 receiver recovers clock and data from the selected inputs
after 20 dB amplifiers. If required, the clock adapter converts input E1 clock
signals (2.048 MHz) to DS1 signals (1.544 MHz) for use by the track and hold
cards.
5.1023 Receive
Framers
Clock and data from the two selected inputs are fed to two framers. The
framers are periodically read by the microprocessor to obtain counts of LOS
events, OOF/AIS events, BPVs, and CRC/FBE code errors. This information
is sent to the 54550 card for storage and later reporting and, if any counts
exceed certain thresholds (refer to Table 4-A), the corresponding front panel
yellow LED is turned on.