Specifications

162
www.ensembledesigns.com tel [phone]
element. This keeps the signal symmetrically balanced
so that its DC content is zero. And it also means that the
timing picko point is now at the point where the signal
crosses blanking and is no longer subject to variation with
amplitude. This makes Tri-Level Sync a much more robust
signal and one which can be delivered with less jitter.
USB – The Universal Serial Bus, developed in the computer
industry to replace the previously ubiquitous RS-232
serial interface, now appears in many dierent forms and
with many dierent uses. It actually forms a small local
area network, allowing multiple devices to coexist on a
single bus where they can be individually addressed and
accessed.
WSS – Wide Screen Signaling is used in the PAL/625 video
standards, both in analog and digital form, to convey
information about the aspect ratio and format of the
transmitted signal. Carried in the vertical interval, much
like closed captioning, it can be used to signal a television
receiver to adjust its vertical or horizontal sizing to reect
incoming material. Although an NTSC specication for WSS
exists, it never achieved any traction in the marketplace.
Word Clock – Use of Word Clock to genlock digital audio
devices developed in the audio recording industry. Early
digital audio products were interconnected with a massive
parallel connector carrying a twisted pair for every bit in
the digital audio word. A clock signal, which is a square
wave at the audio sampling frequency, is carried on a 75
ohm coaxial cable. Early systems would daisychain this
44.1 or 48 kilohertz clock from one device to another
with coax cable and Tee connectors. On the rising edge of
this Work Clock these twisted pairs would carry the left
channel, while on the falling edge, they would carry the
right channel. In most television systems using digital
audio, the audio sample clock frequency (and hence the
'genlock' between the audio and video worlds) is derived
from the video genlock signal. But products that are purely
audio, with no video reference capability, may still require
Word Clock.
YUV – Strictly speaking, YUV does not apply to component
video. The letters refer to the Luminance (Y), and the U
and V encoding axes using in the PAL composite system.
Since the U axis is very close to the B-Y axis, and the V axis
is very close to the R-Y axis, YUV is often used as a sort of
shorthand for the more long-winded “Y/R-Y/B-Y”.
Y/Cr/Cb – In digital component video, the luminance
component is Y, and the two color dierence signals are Cr
(R-Y) and Cb (B-Y). Y/Pr/Pb – In analog component video,
the image is carried in three components. The luminance
is Y, the R-Y color dierence signal is Pr, and the B-Y color
dierence signal is Pb.