Studio Technologies M233-01151 - Manual (Page 16)

Issue 5, November 2014 Model 233 User Guide
Page 16 Studio Technologies, Inc.
Intercom Interface
The Model 233’s intercom interface is
designed to directly connect with standard
single- and dual-channel party-line inter-
com lines. The one or two audio signals
provided by the intercom line can serve as
audio sources for the headphone outputs.
Each signal can be individually assigned
to the left channel, the right channel,
or both the left and right channels. The
Model 233 can also be configured to send
talkback audio to either or both of the in-
tercom channels. In addition, the intercom
line can provide the DC power required to
operate the Model 233’s circuitry.
An intercom line is connected to the
Model 233 by way of a 3-pin female XLR
connector which is located on the back
panel. The mating connector (male)
should be wired so that common is on
pin 1, DC with channel 1 audio is on pin
2, and channel 2 audio is on pin 3. With
single-channel intercom lines common
is on pin 1, DC power is on pin 2, and
audio is connected to pin 3.
The Model 233’s intercom interface is
directly compatible with broadcast and
production party-line intercom lines as-
sociated with systems from manufactures
such as RTS and Clear-Com. Intercom
lines associated with other systems
should be equally compatible. RTS TW-
series systems are normally interfaced
using 3-pin XLR connectors. These con-
nectors are wired with common on pin 1,
DC power and channel 1 audio on pin 2,
and channel 2 audio on pin 3. Most Clear-
Com party-line systems are single-channel
with common on pin 1, DC power provid-
ed on pin 2, and audio provided on pin 3.
The DC power supplied by the connected
intercom line is generally sufficient to
operate the Model 233’s circuitry. The
acceptable input range is 24 to 32 volts,
with a required current of 125 milliam-
peres. Note that the specified input volt-
age is given when measured directly at
the Model 233’s intercom input connec-
tor (with the connector terminated on the
Model 233) and not at the source of the
intercom system’s power.
External Power Input
An external source of 24 volt DC power
can be connected to the Model 233 by
way of a 2.1 x 5.5 mm coaxial power jack
which is located on the back panel of
the unit. The center pin of the jack is the
positive (+) connection. While the require-
ment for the external source is nominally
24 volts, correct operation will take place
over a 20 to 30 volt range. The Model 233
requires 90 milliamperes at 24 volts DC
for correct operation. Included with each
Model 233 is a 24 volt DC external power
supply. The power supply’s DC output
cable has been terminated with a Switch-
craft® S760K coaxial power plug. This
“locking” type of plug correctly mates with
the Model 233’s 24 Vdc input jack. The
locking feature is important, allowing
the external power source to be securely
attached to the Model 233.
As previously discussed in this user guide,
an intercom line connected to the Model
233 can serve as the unit’s power source.
Alternately, an external 24 volt DC source
can be connected. For redundancy, the
intercom line and the external source
can be connected at the same time. If
one of them becomes inoperative the
remaining source will provide power for
the Model 233.