Crystal Vision
Introduction
TANDEM-110 User Manual R1.8
10
07/07/2010
SDI PLL function
There is a single module, like a "time base corrector" that may be inserted into either SDI
1 only, SDI 2 only, or left out of circuit (OFF).
The SDI signal accumulates an ever-increasing amount of jitter as it progresses through
an SDI installation, and as it passes through most equipment in its path. To minimise this
effect, TANDEM-110 has an SDI crystal controlled re-clocker which sets the output SDI
signal to the same mean frequency as the input, but re-clocked by a crystal controlled
Phase Locked Loop [PLL]. This produces extremely low jitter in the SDI output, even in
the presence of a very high level of jitter in the incoming signal. Typically, jitter of 1 or 2
nanoseconds peak to peak will be reduced to a few hundred picoseconds.
The PLL can be placed in either an SDI 1 or SDI 2 input path prior to processing, so all of
the functions of that side, as well as the SDI output, benefit.
Factory defaults
A facility is provided at the card-edge to load ‘factory defaults’ for routing, delay and
preset data into TANDEM’s non-volatile memory. It is strongly recommended that the
appropriate factory defaults be loaded after any of the following:
a change of Mode
whenever sub-PCB cards have been changed
at any time card edge or other menus appear corrupted
Please refer to section 5.2 for details of the available factory defaults that may be recalled.
Note:
Always check that the appropriate groups are selected for embedding or de-embedding
after loading defaults (refer to section 5.3 for card edge controls).
Monitoring
TANDEM-110 is equipped with two monitoring outputs:
analogue headphone output
analogue rear connector output
The rear connector output is fed from a monitoring ‘bus’ that may be switched between
silence and a copy of the analogue headphone output.
The rear connector monitoring may be used to extract a ‘breakout’ ‘monitoring quality’
output, even when an output option card is not fitted.
The analogue output can be manually selected as adjacent pairs or routed using the in-
built routing to extract non-adjacent signals from the same group.
External reference
Digital output option cards may be used with an external word clock or AES reference.
Link jumpers are provided on the digital option cards to select 110 Ohm, HiZ or 75 Ohm
impedance.
