Coral FlexiCom 6000 Installation Manual
Common Control Cards
8-69
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GC Gr
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Clock Selection
The external clock synchronization selector monitors the 4 inputs (two are in current
use while two more may be added in future configurations) for the presence of an 8.0
kHz clock signal which may be derived from a digital trunk card. A primary and
secondary clock source may be defined in the system database, to synchronize the
PCM clock of the 32GC card to the digital trunk. In the absence of an external clock
source, the 32GC card always reverts to an internal clock. Clock failure is reported in
the Program Interface.
Digital Tone Generator
The digital tone generator generates the audio call progress tones used to notify the
caller of the status of the call. The stored tone patterns are output directly to the digital
PCM bus when required.
The system automatically verifies, upon system initialization, that the tones are
appropriate for the system as configured and overwrites the flash tone device on the
32GC card as appropriate.
PCM Streaming
Each PCM stream operates at a data rate of 8.192 Mbps. Each PCM stream consists of
transmit and receive signals, each of which are divided into 128 time slots. Each time
slot is eight bits wide, sampled every 125 µs, or 8,000 times per second. This rate
matches both A/µ law PCM voice transmission rates to facilitate complete digital
integration with the local telephone network.
The time switching matrix, acting on command by the system processor, is responsible
for forwarding PCM voice samples from an incoming transmit time slot assigned to
one port to a complementary outgoing receive time slot for the recipient port.
Using Time Slots
A call between two ports requires one transmit and one receive time slot on a single
peripheral highway. Therefore, the 32GC card is capable of establishing calls between
any 2K ports and any other 2K ports, on any of the 16 peripheral shelves, for a max of
2K calls. This switching matrix allows for a Constant Frame Delay operation mode.
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Circuit Description
