Telos ZephyrExpress - Manual (Page 180)

APPENDIX 11-13
SPIDs
Service Profile Identification (SPID) numbers are required in all but one the AT&T proto-
cols. This number is given to the user by the phone company and must be entered cor-
rectly into ZephyrExpress in order for the connection to function. SPIDs usually consist
of the phone number plus a few prefix or suffix digits. There is frequent confusion be-
tween phone numbers and SPIDs, even among telco personnel. While the SPID fre-
quently includes the corresponding phone number, this is not necessarily the case.
The intention of the SPID is to allow the Telco equipment to automatically adapt to vari-
ous user requirements by sensing different SPIDs from each type or configuration of
user terminal. None of this matters with our application, but we must enter the SPIDs
nevertheless. BellSouth has proposed, and most of the other telephone companies have
agreed to implement, a standardized SPID for new National ISDN installations. They an-
nounced this would be phased in during 1996. As of this writing, it has generally been
implemented by most telcos. The standard is area code+phone number+0101
(XXXYYYZZZZ0101).
Unless you are using the AT&T PTP protocol, your Telco service representative should
give you one SPID for each B channel you order. Don’t let the phone company installer
leave without providing you with the phone numbers of your B channels (called Direc-
tory Numbers, or DNs) and your SPIDs!
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 enabled for voice and/or data
use. Phone 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 pos-
sible but irrelevant to our needs.)
CSD is required for ZephyrExpress connections. Even though you may be sending voice,
the codec bit-stream output looks like computer data to the phone network.
CSV is for interworking with standard voice phone service and allows ISDN to call to
analog phone lines and phones. ZephyrExpress allows outgoing voice calls on either of
the channels if you have CSV. ZephyrExpress’ voice capability exists on both channels.
Thus you can make calls to any normal telephone number on one channel while a pro-
gram is being transmitted on the other. This is a feature you may want to use.
You will be ordering an ISDN BRI 2B+D line with CSD and CSV (sometimes called alter-
nate CSD/CSV) available on any B channel.
56/64kbps
All ISDN BRIs have a 64 kbps per channel capacity and almost all local calls operate at
this rate. Some long distance connections, however, operate at only 56 kbps.
ZephyrExpress provides standard rate adaptation (officially known as CCITT V.110) from
56 to 64 kbps when required. Bit rate adaptation happens automatically within Zephyr-
Express depending upon the rate of an incoming call.
In our experience, the only sure way to know the capacity of a given connection is to try
it, first at 64 kbps and then at 56 kbps if the higher rate fails.