Circuit Card Descriptions
22. SWITCH MATRIX CARD
22.01 The Switch Matrix Card resides in a dedicated card slot directly
to the right of the MCC in the control bay of the
672-port
SX-200 DIGITAL PABX. It expands the DX switching matrix, the static
non-volatile RAM, and the resources of the 7720 Digital Signal Proces-
sor. The card measures approximately 325 mm x 366 mm (12.8” x
14.4”).
Facilities
22.02 The Switch Matrix card provides:
0
24 x 24 link DX array
0
Digital Signal Processor
l
Dial Tone Filter
0
Ringing Reference Generator
a
8
Kbytes
Non-volatile Static RAM
DX Array
22.03 The DX Array on the Switch Matrix Card consists of a 24 x 24
link switching array provided by 9
Mite1
DX chips with balanced
drivers and receivers.
Ringing Reference Generator
22.04 The Digital Signal Processor generates PCM data corresponding
to a
20Hz
sine wave, which is passed through the DX array. A
codec
then converts the PCM to analog. This 20 hz signal is then
filtered and distributed via the backplane to the Bay PSU, which con-
tains a ringing amplifier.
Non-volatile Static RAM
22.05 Any time the user enables a function the changed data
(extension number, type of forwarding) must be saved in a
non-volatile memory so that it is not lost on power down or system
failure. The Static RAM acts as a buffer for this sort of data. As the
data accumulates, finally filling up the buffer, it is then transferred to
disk. This reduces disk running time, increasing the disk drive’s life-
span. During power-off periods, the static RAM is powered from a
large capacitor, providing 72-hour holdover time.
WARNING
THE SWITCH MATRIX CARD MUST NOT BE INSERTED OR REMOVED
WITH THE POWER ON. DAMAGE TO
ONBOARD
CIRCUITS MAY RE-
SULT.
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