Studio Technologies IFB Plus 2001 - Manual (Page 9)

Model 2 User Guide Issue 7, November 2001
Studio Technologies, Inc. Page 9
Program audio is muted whenever an
interrupt takes place. A sophisticated
analog switch is used to give a noise-free
mute with absolutely no clicks or pops! If
desired, a program “dim,” rather than a full
mute can be implemented by adding two
resistors to the Model 2’s circuit board.
Compressor/Limiters
Each IFB channel contains a studio-quality
compressor/limiter. The compressing
function evens out variations in the inter-
rupt audio signals. The limiting function
smoothly controls peak signal levels.
Together, they make talent cues more
intelligible and prevent abnormally high
signal levels from reaching a user’s ears.
The resulting audio quality is very, very
good.
Signal Routing
In the standard configuration, only inter-
rupt audio is routed through the compres-
sor/limiter before it is sent to the talent
amplifier output, line output, telephone
interface 2, etc. Program audio is routed,
via the program audio level control and
mute/dim circuit, directly to the talent
amplifier output, line output, etc. Thus
the dynamic range of the program signal
is not altered. Some installations may
benefit from the program audio being
routed through the compressor/limiters.
This “leveling” action can improve intelligi-
bility of the program audio, especially in
areas of high ambient noise such as news
remotes or sporting events. Resistor
positions on the Model 2’s circuit board
allow a technician to change the audio
flow, routing program audio via the com-
pressor/limiters. The only downside is that
this rerouting greatly limits the ability to
adjust the relative level of the program
audio versus the interrupt audio. This is
because the compressor/limiter function
reduces the dynamic range of the pro-
gram audio. As the program level control
is turned “up,” the compressor acts to
reduce the signal level! Also, some users
may find the compressed program signal
more fatiguing due to the higher average
audio level.
Telephone Interfaces
The Model 2 contains two telephone
interfaces. Both interfaces can be used
to bring audio into the Model 2 from the
outside world. These two audio signals
can be independently assigned as pro-
gram sources for IFB channels 1 and 2,
as well as being used as an input source
for the voice operated (VOX) interrupt
function. Each telephone interface has
a receive level trim potentiometer that
is accessible via access holes in the front
panel. The large variations one finds in
telephone line signal levels make “on
the fly” level trimming a useful feature.
In addition to receiving audio, telephone
interface 2 can be used to originate an
IFB feed. A switch selects if audio will
be received from the outside world, or
if audio from IFB channel 1 or 2 will be
sent out the interface.
The two telephone interfaces contain
a unique feature which allows two very
different types of telephone “lines” to be
correctly interfaced. Each interface can
be independently set to operate in either
the telephone-line mode or the standard-
audio mode. A telephone line has the
profile of being a 2-wire, DC-biased (nor-
mally –48Vdc) circuit provided by a local
telephone company. A standard audio
signal could be provided by, for example,
a fax adapter associated with a cellular
telephone.