Telos Zephyr Xstream - Manual (Page 149)

USER’S MANUAL
Section 7: ISDN BASICS 137
Z
ZEPHYR CLASSIC VS XSTREAM COMPARISON!
Most versions of the Zephyr Classic can operate without Directory Numbers. Zephyr Xstream
requires the DNs be present to receive incoming calls.
Multiple Subscriber Numbers (MSNs)
MSNs perform the same function when the ISDN protocol used is ETS 300 (Euro ISDN) or INS 64
(Japanese ISDN). In this case, use of the MSN is entirely optional. If no MSNs are entered, the
first call to any of the numbers associated to the ISDN circuit will ring in as “line 1” if that “line”
is idle. If “line 1” is in use the call will ring in on “line 2”. This is precisely the same behavior as
when a line with the “AT&T Custom PTP” protocol is used.
Long-Distance Digital Connectivity
Long‐distance connectivity is routinely available in most parts of the USA from carriers such as
AT&T, Sprint, and Verizon. Connectivity between any two given points is somewhat variable.
The “dial 1+” default carrier may be chosen at the time you order the line, just as with
traditional voice lines. Also, just as with voice lines, you may choose a carrier on a per‐call basis
by prefixing the number with the 1010XXX carrier selection code.
You must dial the full number, including the 1 or 011 + country code following the prefix.
Some long‐distance connections are limited to 56kbps/channel. This limitation is becoming
more rare. There is no certain way to know in advance. Occasionally, some connections may
work at 64Kbps and not 56Kbps. Therefore, you may need to try both.
The Zephyr Xstream provides standard rate adaptation (officially known as ‘CCITT V.110’) from
56 to 64 kbps and vice versa when required. Bit rate adaptation happens automatically within
the Zephyr Xstream depending upon the rate selected by the calling party. Since the Zephyr
Xstream cannot communicate at both rates simultaneously, it will ignore rate adaptation
information on the second incoming call remaining at the rate set for the prior call.
In our experience, the only sure way to know if a connection given between to particular points
will work is to try it, first at 64kbps and then at 56kbps if the higher rate fails.
i
ISDN TIP!
Not all carriers can handle “Circuit Switched Data” (CSD) connections at all. This type of
connection is what makes real-time low-delay audio transmission possible, and is required.
For the latest information, check Appendix 10 (Ordering ISDN in the USA & Canada).