Telos Zephyr Xport - Manual (Page 40)

ZEPHYR XPORT
USER’S GUIDE
30
CHAPTER 4 - FREQUENTLY ASKED QUESTIONS
4 Frequently Asked Questions
We cover general questions about the Xport and the technology involved here. If you
have questions related to operational issues, or need to troubleshoot a problem, see
Section 5 (What to do if…).
Is Xport a “POTS codec”?
Yes and no. Xport is for the field, and uses POTS (Plain Old Telephone Service) analog lines or
ISDN lines (using the optional ISDN interface). But, you will be connecting with a Zephyr Xstream
at the studio using an ISDN line – the same one you probably already have.
Are there advantages to using ISDN, in addition to being able to use the same Telco line and Zephyr
codec equipment at the studio?
Yes, certainly. Modems work best on lines that are noise and distortion- free. They are also
sensitive to the echo and noise inevitably caused by the hybrids and converters needed to adapt
analog lines to the digital switching and transmission used within the Telco network. When you
have a digital ISDN connection at the studio side, you get rid of much of the problem, by removing
two hybrids and eliminating any possible noise problems from half of the link.
Older POTS codecs confined to using analog at both ends require a total of 4 hybrids in the path, each of
which can cause modem problems from reflections and from the analog/digital conversion noise that is
added each time. Noise can be induced into two analog lines.
Zephyr opens a pure digital connection on the studio side, so half the trouble is eliminated.
The combination of ISDN + the special DSP- based modem technology means that Xport can cut
through line problems that other codecs cannot. Internet Service Providers have used this
approach for years.