Studio Technologies 770 - Manual (Page 17)

Model 770 User Guide Issue 1, October 1997
Studio Technologies, Inc. Page 17
Model 770
An input audio signal is expected to be in
the range of –15dBu nominal.
In this paragraph we’ll provide examples
of two hypothetical sources, and how they
might be connected to the Model 770’s
telco interface. The first source is a signal
from a satellite telephone system. It’s a
“wet” telco signal because it has a DC
voltage present, with standard high-volt-
age ringing to indicate that a call is com-
ing in. From an operational standpoint
auto-answer is not desired. In this case
connect tip and ring from the satellite
telephone system to pins 3 and 4 (red and
green) of the source modular jack, and
connect a jumper wire across pins 1 and
6 (white and blue). Now when this jack is
connected to the Model 770’s telco inter-
face, of course using a 6-conductor cord,
the telco interface’s operating mode will
remain in telco, but auto-answer will be
defeated. Our second example is a signal
is a cell-phone fax adapter. It’s a “dry”
audio signal, not having a DC voltage
associated with it. In this case the signal
is terminated on pins 3 and 4 (red and
green) of the source modular jack, and a
jumper wire is connected across pins 2
and 5 (black and yellow). When this jack
is connected to the Model 770’s telco
interface the operating mode will automati-
cally switch to standard audio.
Talent Amplifier Output
The talent amplifier output is designed to
supply power and audio signals for up to
four Studio Technologies’ Model 32 or
Model 33 Talent Amplifiers. The term
“wet” is associated with the talent amplifier
output because, along with analog audio
signals, DC power is present . The talent
amplifier output uses a single male XLR-
type connector for interconnection; pin 1
is common, pin 2 is +22Vdc modulated
with IFB audio, and pin 3 is “dry” audio.
The audio signal associated with pin 3 is
configured using DIP switches located on
the back panel. Refer to the Configuration
section of this guide for details.
It is expected that the talent amplifier
output will be wired to the vehicle’s input/
output connector panel. As the Model 32
and 33 Talent Amplifier units have “loop
thru” connectors, an input/output panel
does not need numerous “mults” of the
signal—two should be sufficient. As DC
power is present, it is recommended that
the talent amplifier output signal not be
wired by way of a patch bay.
IFB Line Output
The IFB line output has been optimized
for connection to devices located external
to the vehicle. This “ruggedized,” trans-
former-coupled output has a nominal level
of +4dBu. It is considered a “dry” output
as DC power is not present. It is expected
that the IFB line output be wired, via the
patch bay, to the vehicle’s input/output
connector panel. A 3-pin male XLR-type
connector is used for interconnection.
Prepare the mating connector (female)
so that pin 2 is high (+ or hot), pin 3 is
low (– or cold), and pin 1 is shield.
Should a line-level IFB signal need to be
connected to a device located within the
vehicle, such as a wireless IFB transmitter,
it is better to use one of the configurable
outputs, rather than the IFB line output.
Sonically there is little difference, except
that the IFB line output is a well-protected,
transformer-isolated output that is best
kept available exclusively for connecting to
devices external to the vehicle. In this way
externally generated noise, static, or