Studio Technologies 770 - Manual (Page 10)

Issue 1, October 1997 Model 770 User Guide
Page 10 Studio Technologies, Inc.
Model 770
Becoming increasingly common for use
in IFB applications, these telephones often
don’t provide a “wet” interface, but do
exhibit the audio levels of a conventional
telephone line.
When the interface is set to the telco
mode, full loop current monitoring and
control is implemented. A front-panel
switch allows the telephone line to be
seized (answered) or disconnected (hung
up). The interface will automatically hang
up if a telephone-company-provided
disconnect signal is received. An audible
signal and LED indicator are active when-
ever “ringing” voltage is present. An auto-
answer function is also provided.
When the interface is set to the standard
audio mode, the loop-current-specific
features are disabled, and the interface
operates as a transformer-coupled bal-
anced audio input. The input level sensitiv-
ity is optimized for use with telephone-type
audio signals.
IFB Outputs
The IFB section contains four outputs:
talent amplifier, line, intercom link, and
monitor. The talent amplifier output is a
“wet” output that supports the connection
of belt pack modules from Studio Tech-
nologies. A single XLR-type cable links
the talent amplifier output with up to four
Model 32 or Model 33 Talent Amplifiers.
The talent amplifier output provides DC
power, along with two audio channels.
The first audio channel provides IFB au-
dio, while the second is configurable.
Using DIP switches, located on the back
panel, three audio sources are available:
the mixer section’s main and AUX bus,
and IFB program only. This allows a broad
range of applications to be supported.
The line output is transformer coupled,
with a nominal level of +4dBu. Well pro-
tected from damage due to externally
generated signals, it is suitable for con-
nection to devices remote from the Model
770. The intercom link output allows the
direct connection of IFB audio into broad-
cast intercom systems. The output imped-
ance and signal level was carefully de-
signed to eliminate the need for external
“pads,” isolation resistors, or blocking
capacitors.
While the Model 770’s monitor section
allows switch-selectable monitoring of the
IFB signal, for efficient broadcast opera-
tion it is often imperative that the IFB
signal be monitored continuously. This is
why the IFB section provides a separate
line-level monitor output and associated
level control. With this output, the operator
can have a monitor loudspeaker dedi-
cated exclusively to IFB.
Monitor Section
The Model 770’s monitor section provides
separate outputs, along with an associ-
ated level control, to allow connection of
a monitor amplifier and headphones. In
addition to monitoring the main, AUX,
and IFB audio buses, provision has been
made for monitoring two external audio
sources. These monaural inputs are in-
tended to be connected to off-air, micro-
wave, or satellite receivers.
Multiple sources can be simultaneously
selected for monitoring. This can prove
useful by allowing, for example, an opera-
tor to simultaneously monitor a local mix
and an externally provided mix-minus
signal.
A mechanical VU-type meter provides a
“user-friendly” indication of audio-signal