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Caller ID support on both ISDN and POTS lines.
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Support for up to twelve controllers.
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VX control protocol for compatibility with Telos VSet, VX Producer, and third-party call
control software applications.
1.3 Integrated Service Digital Networks (ISDN)
The iQ6 works with either traditional analog Telco lines or with ISDN (Integrated Services
Digital Network). We recommend ISDN service for telephone connections whenever possible.
There is no comparable technology for getting audio to and from the public telephone network.
We provide plenty of advice right here in this manual and live support by people with years of
ISDN experience. (Thousands of Telos ISDN interfaces and Zephyrs are deployed around the
world!) Currently, the dial-up telephone network is nearly entirely digital. Only the “last mile”
copper connections from the telephone Central Office exchange to the customer’s site remain
with the archaic analog scheme. ISDN offers us a way to link the studio directly into the Telco
digital infrastructure without the usual impairments of analog connections. iQ6 continues the
digital path with the use of the Livewire audio connection to the iQ console.
While the application of digital signal processing to the problem of separating announcer
and caller audio – pioneered by Telos and used in all of our telephone interfaces – has made
a dramatic improvement over analog-only hybrids, using digital phone lines for on-air calls
further improves performance for several reasons:
1.
Exceptional send-to-receive isolation.
Traditional analog phone lines multiplex both
speech directions in order to use a single pair of wires for a conversation. This causes
what’s referred to as ‘leakage’ – when the announcer’s audio is present on the hybrid
output, creating an annoying ‘hollow’ or ‘tinny’ sound. Telos digital adaptive hybrids
reduce this problem. But ISDN offers independent and separated signal paths, so our
hybrids only have to operate on the far-end analog line, if any. The result is much lower
leakage.
2.
Higher send levels.
We don’t have to be concerned about regulations designed to prevent
crosstalk on analog lines, so we can increase send-to-caller levels.
3.
Lower distortion.
The analog-digital conversion chips used in telephone central offices
are poor compared to the converters used in professional audio equipment. Fidelity
is not an important consideration when telephone equipment designers choose parts
for this function. In a professional interface for studio applications, we can afford to
design-in much better converters. Noise-shaping functions permit a larger word-length
converter to provide significantly better distortion and signal-to-noise performance.
4.
Lower noise.
Because they are digital, ISDN lines are not susceptible to induced noise.
Analog lines are exposed to a variety of noise and impulse trouble-causers as they snake
across town on poles and through your building. Hum is the main problem, given most
lines. Digital lines convey the bits precisely and accurately from the network to your
studio equipment without any perturbation – so the audio remains clean. Even when the
caller is using an analog phone line, the digital connection on the studio side makes for
noticeably lower noise and better overall quality.
5.
Higher gain and reduced feedback during multi-line conferencing.
When conferencing
is required on analog circuits, hybrids are needed to separate the two audio paths in
order to add gain in each direction. When the gain around the loop exceeds unity, the
unpleasant result is feedback. With digital telephone lines, the hybrid function is more
effective – and more reliably so across a variety of calls. That means more gain can be
