Studio Technologies 45DC - Manual (Page 20)

Issue 1, January 2015 Model 45DC User Guide
Page 20 Studio Technologies, Inc.
sample rate can easily transport a 20 kHz
signal.
When the Model 45DC detects DC on the
audio path (pin 3 of the back-panel inter-
face connector) it will digitally generate
a 20 kHz tone and mix (sum) it with any
audio signals present on the associated
Dante output (transmit) channel. Detection
circuits in the Model 45DC’s Dante input
(receive) audio paths continually monitor
for the presence of a 20 kHz tone. If this
signal is detected (in the digital domain)
it will cause a DC voltage to be applied to
the audio path of the associated party-line
interface circuit. When the 20 kHz signal
is no longer present the DC voltage will
be removed. The 20 kHz-to-DC translation
takes place automatically with no configu-
ration required. This method is very use-
ful for a number of reasons. It allows two
Model 45DC units that are interconnected
in a point-to-point manner to transport both
audio and call signals between them. It will
also allow the support of call signals be-
tween a Model 45DC (supporting two sin-
gle-channel Clear-Com party-line circuits)
and a Model 45DR (supporting a 2-channel
RTS party-line circuit). And finally it will al-
low equipment that’s capable of transport-
ing 20 kHz call signals associated with RTS
party-line circuits, such as RTS ADAM OM-
NEO ports, to send and receive DC-based
call signals associated with single-channel
Clear-Com party-line devices.
Note that digital filters in the Model 45DC’s
firmware prevent essentially all information
above 10 kHz from being sent to the party-
line audio channels. This helps to ensure
that the hybrid circuits provide a “deep”
null as was as keeping the 20 Hz call signal
from each party-line audio path.
Common Ground
The Model 45DC provides two independent
single-channel party-line intercom interfaces.
These interfaces can be connected to two
sets of user devices, two existing party-line
intercom circuits, two channels from an
external party-line intercom power supply,
or any combination thereof. An important
thing to remember is that the power source
and audio channel connections associated
with the Model 45DC’s two single-channel
party-line interface channels share a
common ground. This is as expected but
does provide one application limitation.
The two interfaces are not intended to
interconnect (bridge) two intercom circuits
that are isolated from each other. If this
is done through the linking of the pin 1
connections on the Model 45DC’s two
3-pin XLR connectors one can expect hum,
noise, or other audio artifacts to be created.
This would be the result of the potential
difference that would typically be found on
two separate party-line intercom circuits. If
this linking with isolation function is required
a product such as the Clear-Com TW-12C
would be necessary.
3-Position Header
An internal 3-position header connector
allows support for an alternate cover. The
cover, purchased as an option, has an
Anton-Bauer QR-Gold battery bracket
that is electrically wired in parallel with the
4-pin XLR DC input connector. The header,
located on the Model 45DC’s printed circuit
board, is Molex® part number 22-23-2031.
It mates with Molex housing number 22-01-
3037. To make the interconnection, separate
crimp terminals are attached to three loose
wires and then “snapped” into the housing.
Molex part number 08-50-0114 specifies
crimp terminals that are appropriate for 22