Connecting telephone lines – Studio Technologies IFB Plus 2001 User Manual

Page 15

Model 2 User Guide

Issue 7, November 2001

Studio Technologies, Inc.

Page 15

20Hz to 20kHz. This makes using one of
the IFB channels as a four input, one
output audio source selector for an uplink
application completely valid. Let the
Model 2 become a useful part of your
facility’s “bag of tricks!”

Connecting Telephone Lines

Words of Caution: As with any product,
installing the Model 2 requires a safety
first approach.

Never install telephone wiring
during a lightning storm. Never
install telephone jacks in wet

locations unless the jack is specifically
designed for wet locations. Never touch
non-insulated telephone wires or terminals
unless the telephone line has been dis-
connected at the network interface. Use
caution when installing or modifying
telephone lines.

The Model 2 contains two telephone
interfaces which can be individually con-
figured to allow connection to a telephone
line or to a standard audio signal. A tele-
phone line is designated as such if it has
a DC bias current associated with it. This
type of signal is sometimes referred to as
a “wet” signal. A standard audio signal
is one that is isolated from any source of
DC voltage. Some fax adapters associated
with cellular telephones provide this type
of “telephone” line. A standard audio
signal is sometimes referred to as a
“dry” signal. While this sounds confusing,
contemporary applications sometimes
refer to both types of signals as “telco.”
To a large production vehicle that pulls up
to do a two-week golf tournament, a telco
line is one provided by the local telephone
company on an RJ11 jack. To a mobile
ENG vehicle, a telco signal might come

from a cellular telephone which in most
cases is a standard audio signal.

Here is a review of the important features
of the Model 2’s telephone interfaces:

Interface 1
• Telephone line or standard audio mode

select switch on back panel

• Used to receive audio only
• Receive audio used as program and/or

VOX source

• Front panel ±8dB receive level trim pot
• Switch allows manual off-hook and

hang-up (telephone line mode)

• Auto disconnect upon break in loop

current (telephone line mode)

• Operating mode and loop current

status LEDs

Interface 2
• Telephone line or standard audio mode