Studio Technologies IFB Plus 2005 - Manual (Page 13)

Model 2 User Guide Issue 8, December 2005
Studio Technologies, Inc. Page 13
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, termi-
nate on an access panel of some sort. This
will make rapid termination with telephone
company-provided lines. Because 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 interfaces are compatible with
balanced or unbalanced signals. No shield
connection is associated with the telephone
interfaces. Audio signals should be con-
nected to the telco interfaces, via a modular
jack and cable, using shielded cable, with
the shield wire connected to the appropri-
ate 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 +4 dBu professional audio
standard. The nominal receive signal level is
expected to be –15 dBu, the transmit level
is –6 dBu. Trim pots are associated with
both interfaces, allowing the receive level
to be adjusted over a ±8 dB range. Special
precautions may need to be taken when an
interface is set for standard audio mode and
+4 dBu signals are going to be connected.
These would include the use of an audio at-
tenuator or “pad” for connecting receive au-
dio, 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 microphone
input, a balanced line-level input, two lighted
pushbutton switches, and related circuitry to
access the two IFB channels. Power is pro-
vided by the Model 2, so an external power
source is not required. Nine-pin D-submin-
iature connectors link the Model 22 with the
Model 2 Central Controller and, if desired,
another Model 22. A 5-position screw termi-
nal strip allows connection of a Studio Tech-
nologies Model 11A gooseneck microphone
or a line-level signal.
There are three mounting methods ap-
propriate 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 the rack adapter.
Plenty of room remains on the right side of
the rack adapter, allowing you to add cus-
tom switches, lights, or jacks as your instal-
lation may require.
The Model 28A Panel Adapter allows the
installation of a Model 22 and a Model 11A
gooseneck microphone in a “cut out” made