Polycom EX Manual De Referencia

Integrators’ Reference Manual for ViewStation EX, ViewStation FX, and VS4000

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For outgoing calls, the system uses the lowest-numbered available 
channel (1-23 for a PRI T1 and 1-30 for a PRI E1). If an additional 
channel is needed, the system chooses the next higher-numbered 
channel. For example, if channels 1 through 7 are unavailable, but 8 
is available, the system uses channel 8 to place an outgoing call. If an 
additional channel is needed, the system will use the next available 
active channel in the range (which could be 9, and so on).

For incoming calls, the system uses the highest numbered channel 
that is available. If another channel is needed, the next lower 
channel number is used.

The PRI Status screen for E1 shows 30 channels. However, E1 trunk 
lines have 32 timeslots, numbered 0 - 31. Timeslot 0 is used for 
framing, and timeslot 16 is used for call signaling (the D channel). 
The remaining 30 timeslots are used as bearer (data) channels. 

In call signaling between Polycom equipment and the switch, these 
channels are numbered 1-15, 17-31. But the PRI Status screen 
numbers these channels in the range 1-30. On the PRI Status screen, 
channels 1-15 control the status of timeslots 1-15, and channels 16-30 
control the status of timeslots 17-31

.

All channels should be active for a full T1 or E1 line dedicated to 
your ViewStation FX or VS4000.