Telos Zephyr Xstream - Manual (Page 340)

USER’S MANUAL
Appendix 7 – Ordering ISDN for Countries Using ETS300 (EURO ISDN) 328
CSD and CSV
Recall that each ISDN BRI has two possible B channels. It is possible to order a line with one or
both of the B channels enabled – and each may be used for voice and/or data use. Phone
terminology for the class of service is CSV for Circuit Switched Voice connections and CSD for
Circuit Switched Data connections. (In contrast to PSD, Packet Switched Data, this is possible,
but irrelevant to our needs.)
CSD is used for codec connections. Even though you may be sending voice, the codec’s output
will be in data form and therefore must be handled transparently by the telephone network.
This happens because the Zephyr Xstream indicates that this is a CSD call (over the D channel)
when the call is set up.
CSV is for interworking with voice telephone service, and allows ISDN to interwork with analog
phone lines and phones at the far end. CSV is required when communicating to a Zephyr Xport
that is on a POTS line.
You will be ordering one or more ISDN BRI 2B+D circuits with CSD (required) and CSV on each B
channel. Euro ISDN normally provides both CSV and CSD.
NT1s
The ISDN standard specifies two reference points, the “U” and the “S” interfaces. The U is the
single‐pair (2‐wire) bare copper from the Telco CO. A device called a “Network Termination,
Type 1” converts this to the two‐pair (4‐wire) S interface. The Zephyr Xstream includes a built‐in
NT1. This is for use in the USA & Canada. You should not connect to the U interface in other
countries without first consulting the Telco. They may have regulations against doing so, and
they will probably provide power for remote powering an NT1, and this power could damage
your Zephyr Xstream’s ISDN interface.
The older Zephyr classic units sold outside the USA may only have an S interface. If you plan on
taking those units to Canada or North America you will need to rent or purchase an external NT1
for use while in those countries. One rental source is Silver Lake. See their website at
www.silverlakeaudio.com .
PP vs PMP
The S interface allows for multiple terminals to be connected simultaneously. This is called
Point to Multi‐Point (PMP) operation. When a single terminal is used this is referred to as a
Point to Point configuration (PP).
The Xstream can be used in either environment. If you intend to have other terminals share the
S interface with the Xstream, you should make sure your Telco configures their switch properly
to support this (PMP). You will also need to follow the correct termination rules if you will have
multiple terminals.
Line Deactivation
The Euro ISDN standard allows ISDN BRI lines to be deactivated by the Telecom when not in use.
It is impossible to distinguish a deactivated line from a line that is defective and out of service,