Studio Technologies IFB Plus 2001 - Manual (Page 16)

Issue 7, November 2001 Model 2 User Guide
Page 16 Studio Technologies, Inc.
Setting the mode switches and connect-
ing signals is quite easy. Set the tele-
phone interface mode switches, located
on the back panel, to the desired mode—
either telephone line or standard audio
signal. Use modular telephone cables to
mate the Model 2’s modular jacks (RJ11-
type) with two more RJ11-type jacks.
Technically, the Model 2’s telco interfaces
use 6-position modular jacks with pins 3
and 4 utilized.
If the telephone line mode is selected,
the telco interfaces should, in most cases,
terminate on an access panel of some
sort. This will make rapid termination with
telephone company-provided lines. Be-
cause of the presence of high voltage
ringing signals, it is best not to route tele-
phone lines through an audio patch bay.
If the standard audio mode is selected,
a direct connection to the source device
is acceptable, but connecting it via audio
patch points provides better flexibility. In
the standard audio mode the interfaces
look like standard, transformer coupled
audio inputs. Interface 1 has an input
impedance of 2200 ohms. Interface 2 has
an input impedance of 2200 ohms in the
receive mode, and 700 ohms in the send
mode. In standard audio mode, the inter-
faces are compatible with balanced or
unbalanced signals. No shield connection
is associated with the telephone inter-
faces. Audio signals should be connected
to the telco interfaces, via a modular jack
and cable, using shielded cable, with the
shield wire connected to the appropriate
point at the end opposite of the Model 2.
The shield wire should remain unterminat-
ed at the Model 2’s end.
The telco interfaces are designed to
receive and, in the case of interface 2,
send audio signals at nominal levels
that are correct for telephone circuits,
but which are far lower than the typical
+4dBu professional audio standard. The
nominal receive signal level is expected
to be –15dBu, the transmit level is –6dBu.
Trim pots are associated with both inter-
faces, allowing the receive level to be
adjusted over a ±8dB range. Special
precautions may need to be taken when
an interface is set for standard audio
mode and +4dBu signals are going to be
connected. These would include the use
of an audio attenuator or “pad” for con-
necting receive audio, and the use of a
line amplifier to achieve send gain from
interface 2.
Access Stations
The Model 2 allows the connection of
up to four Model 22 Access Stations. The
Model 22 provides an unbalanced micro-
phone input, a balanced line-level input,
two lighted push button switches, and
related circuitry to access the two IFB
channels. Power is provided by the
Model 2, so an external power source
is not required. Nine-pin D-subminiature
connectors link the Model 22 with the
Model 2 Central Controller and, if desired,
another Model 22. A 5-position screw
terminal strip allows connection of a
Studio Technologies Model 11A goose-
neck microphone or a line-level signal.
There are three mounting methods appro-
priate for the Model 22: the Model 25A
19-inch Rack Adapter, the Model 28A
Panel Adapter, or custom. The Model 25A
19-inch Rack Adapter allows the rapid
installation of a Model 22 and a Model 11A
gooseneck microphone in a single rack
space. Refer to Figure 2 for details on how
the Model 22 is physically positioned in