TELOS TWOX12 USER’S MANUAL
ISDN BRI ORDERING GUIDE FOR USA & CANADA
APPENDIX 7 208
terminology for the class of service is CSV for Circuit Switched Voice and CSD for Circuit
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.
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. Therefore Telos
TWOx12s shipped outside the USA & Canada have the S interface. In the USA & Canada the
NT1 must be provided by the user, and is therefore built-in to the TWOx12’s ISDN terminal
adapter. In this case the “U” (RJ-11) interface is provided.
Terminals and Terminal Types
Any equipment connected to an ISDN line is a ‘terminal’ – whether phone, computer, or
Hybrid. Point-to-point lines support one terminal, while multipoint lines can have up to eight
in some applications.
“Terminal Type” is a parameter sometimes requested by the phone people. The appropriate
value for the TWOx12 varies depending upon protocol and is included on the order forms.
IOC Capability Packages (provisioning package)
More and more Telcos are using ISDN Ordering Code (IOC) capability packages for ISDN
ordering (National ISDN protocol only). If your telephone company uses these you need only
tell them you need IOC package “S” and an RJ-11 style jack. We still recommend that you
fax them these forms as well.
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 called 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 (i.e. the Hot line and the Warm line). Be sure to specify to
your Telco how you expect this to work.
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