Studio Technologies 750 - Manual (Page 15)

Model 750 User Guide Issue 3, May 1997
Studio Technologies, Inc. Page 15
Model 750
Record/Talk Back External
Audio Input
The Model 750 contains an internal micro-
phone which is used by the setup section
for voice recording, as well as by the talk
back functions. In special cases it may be
desirable for an external source of audio
to be used in its place. A ¼-inch 3-con-
ductor phone jack allows the connection
of a line-level signal, with a nominal level
range of –20 to +4dBu.
Prepare the mating connector (plug) so
that tip is signal high (+ or hot), ring is low
(– or cold), and sleeve is shield. With an
unbalanced source connect the tip to high
(+ or hot), and both the ring and sleeve
to shield. If connecting to an unbalanced
source in this manner results in hum or
noise, connect tip to high (+ or hot)
and ring to shield; leave the sleeve
unterminated.
It is intended that a microphone associ-
ated with an intercom system headset will
serve as the external audio source. Inter-
com station’s often provide an amplified,
line-level version of the mic signal. It is
often referred to as a “hot microphone”
output.
A trim potentiometer is associated with the
external audio input, allowing adjustment
of the input sensitivity. Refer to the Con-
figuration section of this guide for details.
Information is also provided on how to set
the front panel DIP switch to select the
external audio input.
Connecting AC Mains Power
The Model 750 is factory configured to
operate from AC mains power of either
100, 120, or 220/240V, 50/60Hz. In most
cases, units shipped to North America
are factory configured for 120V operation
and are supplied with an internal 0.5A,
5 x 20mm fast-acting fuse. Units config-
ured for 100V also utilize a 0.5A fuse. Units
configured for 220/240V operation are
supplied with a 0.25A, 5 x 20mm fast-
acting fuse.
Before connecting the Model 750 to mains
power, determine the actual mains voltage
and confirm that the Model 750 has been
configured correctly. As could be ex-
pected, an incorrect mains configuration
could seriously damage the unit.
Should it be necessary to change the
unit’s operating voltage refer to the Ser-
vice Guide, a separate document available
upon request from Studio Technologies.
Figure 4. Detail of back panel showing voltage
configuration chart