TELOS TWOX12 USER’S MANUAL
ISDN BRI ORDERING GUIDE FOR ETS 300 (EURO ISDN)
APPENDIX 6 203
Switched Data. (In contrast to PSD, Packet Switched Data, which is possible but irrelevant to
our needs.)
CSD is not required for Telos TWOx12 connections. Even though you are sending a stream of
data, the phone network knows to translate this back to analog at the far end due to the call
setup message sent on the D channel when the call is made. If this ISDN BRI circuit will also
be used with an audio codec such as the Zephyr or ZephyrExpress, then CSD should be ordered
as it is required for audio codec calls.
CSV is for interworking with voice phone service and allows ISDN to interwork with analog
phone lines and phones.
You will be ordering one or more ISDN BRI 2B+D circuits with CSV (required) and CSD
(optional) on each B channel. Euro ISDN normally provides both CSV and CSD which is
acceptable.
NT1s
The ISDN standard specifies two reference points, the “U” and the “S” interfaces. The U is the
single-pair bare copper from the Telco CO. A device called a “Network Termination, Type 1”
converts this to the two-pair S interface.
In Europe, Asia, South America, and most of the world the NT1 is always provided by the
phone company, and only the S interface may be on user equipment. If you plan on taking your
TWOx12 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 .
Hunt Groups
Just as with analog lines, ISDN BRI lines can be placed in a “hunt group” where a single
number can be given to callers and the calls will “roll over” from busy channels to idle
channels. This is sometimes referred to as ISG (incoming service grouping) or rollover lines.
This would usually be a requirement for an on-air phone system. You may choose to exclude 1
or 2 channels from the hunt group (ie the Hot line and the Warm line). Be sure to specify to
your Telco how you expect this to work.
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 which is defective and out of
service. If your application is critical you may wish to request that the Telecom disable line
deactivation.
FAXABLE ISDN ORDER FORMS FOR ETS 300
Following form may be used to place orders for ISDN lines in countries using the ETS 300 protocol.
These should give the Telecom all of the information they need.
Complete the top portion of the form and send it to the Telco.
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