Studio Technologies 76D V.2.02 - Manual (Page 40)

Issue 2, June 2009 Model 76D/77 User Guide
Page 40 Studio Technologies, Inc.
for Surround
for the now-synchronized signal. In some
cases it may be useful to connect the
stereo input C direct monitor output to
the input of a signal router, allowing an
entire facility to access the signal.
Model 76D to Control Console
Connections
Figure 6 gives a detailed description of the
signals that connect the Model 76D Cen-
tral Controller to the one or more Model 77
or Model 71 Control Consoles. The Model
76D provides a +12 volt DC power source
for use by the control console’s circuitry.
The DC output is current-limited to mini-
mize the chance that a short-circuit condi-
tion will damage the Model 76D’s circuitry.
An asynchronous, bi-directional data inter-
face links the connected units. The RS-485
hardware connection scheme operates at
a rate of 115.2 kbit/s and uses an 8-N-1
data format. The Model 76D communicates
with each Model 77 and Model 71 unit
20-times per second, receiving button and
rotary level control information and send-
ing LED and 4-digit display status data.
“Hot” Disconnection of
Control Consoles
There’s no problem relocating one or more
Model 77 or Model 71 Control Consoles
while the StudioComm system is operat-
ing. You can disconnect the 9-pin intercon-
necting cable, move the unit (or units), and
then reconnect without issue. Upon discon-
nection of all control consoles the Model
76D Central Controller will mute the moni-
tor output channels as well as saving the
current operating parameters. No clicks,
pops, or other noises will occur when the
Model 77 or Model 71 units are again
connected. The control consoles will go
through their standard power-up sequence
and then normal operation will resume.
Channel Status, User, and
Validity Bits
The non-audio bits that are part of the
AES3/AES3id monitor output channel data
are actively controlled by the Model 76D’s
software. The Channel Status bits use the
Professional Use of Channel Status block.
They indicate a word length of 24 and the
current sample rate. The correct CRC is
also calculated and inserted. The User bits
are always set to 0. When an external tim-
ing reference (sync) source is available to
the system the Validity bits will be set to 1.
The Model 76D’s hardware is capable of
routing the C/U/V bit information from sur-
round input A L/R, stereo input C, and the
sync input to the main logic device (FPGA)
and then on to the digital audio transmitter
(DIT) integrated circuits. This is provided
for future use and is not active at this time.