Telos Zephyr, Руководство пользователя

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Section 5 ISDN 87
The Basic Rate Interface (BRI)
On one ISDN BRI circuit, there are three simultaneous channels: Two 64kbps “bearer”
channels for the transmission of user information and one 16kbps signaling channel for
call set- up and status communication. This is Basic Rate Interface (BRI), 2B+D service.
It can be implemented over most of the millions of standard copper two- wire phone
circuits already in service.
ISDN BRIs are perfectly matched to Zephyr’s transmission capabilities. One channel
provides FM quality mono, while the two channels can carry near- CD quality stereo.
From the perspective of telephone network routing, each B channel appears to be a
separate line with it’s own number and independent dial- out capabilities. Since each
has to be dialed or answered separately, they appear to be “lines” to users also. To
reduce confusion (hopefully) for non- technical users, we refer to a B channel as a “line”
on the Zephyr menus and LEDs.
SPIDS
CURIOSITY NOTE!
While the D channel is always present for signaling, it can, in
theory, be used for packet data connections. ISDN lines where
the D channel is used for signaling only are sometimes
referred to as 2B+0D rather than 2B+D service. D channel
packet service is not widely available and is not used by
Zephyr.
ISDN TIP!
In some cases your ISDN line, while having 2 B channels, will
only have only one phone number. This is the case of the
AT&T Custom PTP protocol. This does not usually present a
problem. This works as if the lines are assigned to a short
“hunt group” i.e.; the first incoming call will be assigned to Line
1, and the second incoming call will be assigned to Line 2. Of
course you have the option of which line to use on outgoing
calls.
DEEP TECH NOTE!
The actual 2 B channels of the BRI are assigned on a per call
basis. Therefore, from a theoretically correct viewpoint, Lines 1
and 2 do not fully correspond to B1 and B2.
ISDN TIP!
European users should disregard all references to SPIDs.
Euro ISDN does not have SPIDs! If your ISDN configuration
requires MSNs they may be entered in the MSN/SPID 1 & 2
screen.