Studio Technologies M233-01151 - Manual (Page 10)

Issue 5, November 2014 Model 233 User Guide
Page 10 Studio Technologies, Inc.
Intercom Interface
Of special note is the Model 233’s sophis-
ticated intercom interface. It’s designed
to work correctly with industry-standard
single- and dual-channel party-line intercom
systems, including those from RTS and
Clear-Com. An intercom line connected to
the Model 233 can serve three functions:
providing cue audio signals to the head-
phone output, allowing talkback audio to
be sent to intercom users, and acting as
a Model 233 power source. Audio signals
present on the single- or dual-channel
intercom line can be flexibly routed to the
stereo headphone output. Talkback audio,
controlled by the two talkback pushbutton
switches, can be sent to either or both of
the intercom channels. Trim potentiometers,
located on the bottom of the unit, allow
adjustment of the talkback-to-intercom
sidetone (null) level.
The ability to listen to one or both pins of
a connected intercom circuit will only be
available when the intercom interface circuit
detects DC voltage on pin 2. This feature
minimizes the chance that objectionable
audio content (i.e., “howls” or “squeals”)
will be routed to the headphone output
when an intercom circuit is not connected.
Audio Quality and Protection
The Model 233’s circuitry is carefully tailored
to provide excellent audio performance.
Professional-quality components are fea-
tured throughout. For reliability all audio
routing is performed using solid-state
devices under microcontroller direction.
In all critical audio paths, “clickless” elec-
tronic switches provide noise-free control.
All audio inputs and outputs make extensive
use of protection components. This limits
the chance of damage from ESD and other
undesirable, yet real-world, hazards.
Power Sources
The Model 233 can derive its operating
power from an intercom line or an external
24 volt DC source. For redundancy, both
power sources can be connected simul-
taneously. An internal switch-mode power
supply ensures that all Model 233 features
are available, including phantom power,
when the unit is powered by either source.
Auxiliary Relay
Model 233 resources include a general-
purpose relay, allowing specialized configu-
rations to be created. Under software con-
trol, the relay can be configured to follow
the state of the main output, talkback 1, or
talkback 2 buttons. Taking advantage of the
back-panel locations provided for additional
XLR connectors, a technician may easily
create functions such as an “on-air” indica-
tor or implement loudspeaker muting dur-
ing talkback function. Special configuration
modes are even included to allow direct
control of the relay using the talkback 1 or
talkback 2 buttons without impacting any
of the Model 233’s audio signals.
Tally Output
Another unique Model 233 feature is the
tally output. It provides an indication, in
the form of a current-limited DC signal, of
the status of the main output. Whenever
the main output is active the tally output
is active. This 3.5 volt nominal, 12 milliam-
peres maximum, signal is capable of direct-
ly lighting an LED indicator or triggering an
external control system. The tally output
is provided specifically for specialized ap-
plications such as television award show
broadcasts where remote monitoring and
control of the main output is required.