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Model 46 User Guide Issue 2, September 2007
Studio Technologies, Inc. Page 27
To display the Model 46’s software version
is very simple. From the powered-down
state, press and hold the auto null button
associated with interface 1. Apply mains
power while continuing to press the but-
ton. The normal power-up sequence will
not occur but instead one LED will be lit in
the column associated with interface 1 and
one LED will be lit in the column associated
with interface 2. As previously described,
these two LEDs represent the unit’s current
software version. While the software version
number is being displayed the LED level
meters will likely display random readings.
This is not a problem and can simply be
ignored. After the software version number
has been “read” the auto null button can
be released. At this time the unit will begin
its normal power-up sequence.
Note that while it’s easy to determine which
software version is loaded into the Model
46 a trip back to the factory is required to
update it. The 8-bit microcontroller that
provides the unit’s logic “horsepower” also
includes internal FLASH memory. This non-
volatile memory is used to store the operat-
ing software (“firmware”). Re-programming
this memory requires using a specialized
programming unit. While not outrageous in
price, it still costs in the range of US$500.
The “programmer” uses a ribbon cable
and socket to interface with a 6-pin “head-
er” on the Model 46’s printed circuit board.
And, as you would guess, once connected,
reprogramming takes only a matter of sec-
onds. But unfortunately the programmer
is not something that would be found in
a typical “field shop” or repair facility.
Not a TW-12B Replacement!
The Model 46 will provide a high level of
performance over its range of intended
tasks. But it’s not intended to act as a
“universal” 2-wire-to-2-wire interface such
as is provided by the venerable Clear-Com
TW-12B. The Model 46’s 2-wire inter-
faces are not isolated from each other;
they share the Model 46’s internal power
supply’s common connection. (The power
supply common point is DC isolated from
chassis and earth ground.) Specifically,
pin 1 on the XLR connector associated
with interface 1’s 2-wire party-line inter-
face is electrically connected to the pin 1
connection on interface 2. This is due to
the fact that both 2-wire party line inter-
faces are capable of supplying DC power
to connected devices. They also use the
resources of a single set of logic circuitry.
And as such they each require access to
the Model 46’s common power supply
circuitry. There’s no doubt that a Model 46
could be used to create a 2-wire-to-2-wire
party line “bridge” by cross-linking the
4-wire inputs and outputs using standard
XLR-type audio cables. But it’s likely that
a significant “ground loop” would be cre-
ated through pin 1 of each of the Model
46’s 2-wire interfaces. While it’s possible
to use a set of special isolation transform-
ers to eliminate the ground loop, that’s
best left to the brave of heart!
Model 72 Interface
And now for a shameless “product plug.”
Studio Technologies, Inc. manufactures
a nifty product called the Model 72 Level
Meter/Interface. A compact, standalone
unit, it can prove very useful when setting
up, maintaining, and troubleshooting inter-
com circuits. It will give a direct indication
of signal levels at any point in a single-
or dual-channel intercom circuit. Check
it out!