Studio Technologies 47A - Manual (Page 26)

Issue 1, September 2014 Model 47A User Guide
Page 26 Studio Technologies, Inc.
To display the Model 47A’s software ver-
sion 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
button. The normal power-up sequence
will occur and then one LED will be lit in
the column associated with FROM 4-wire
channel 1 of interface 1 and one LED will
be lit in the column associated with TO 4-
wire channel 1 of interface 1. As previously
described, these two LEDs represent the
unit’s current software version. After the
software version number has been “read”
the auto null button can be released.
At this time the unit will begin normal
operation.
Note that while it’s easy to determine
which software version is loaded into the
Model 47A a trip back to the factory is
required to update it. The 8-bit microcon-
troller that provides the unit’s logic “horse-
power” also includes internal FLASH
memory. This non-volatile memory is used
to store the operating software (“firm-
ware”). 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 “pro-
grammer” uses a ribbon cable and socket
to interface with a 6-pin “header” on the
Model 47A’s printed circuit board. And, as
you would guess, once connected re-pro-
gramming takes only a matter of seconds.
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 47A 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 47A’s 2-wire interfaces
are not isolated from each other; they share
the Model 47A’s internal power supply’s
common connection. (The power supply’s
common point is DC isolated from chassis
and earth ground.) Specifically, pin 1 on
the XLR connector associated with inter-
face 1’s 2-wire party-line interface is electri-
cally connected to the pin 1 connection on
interface 2. This is due to the fact that both
2-wire party-line interfaces 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 47A’s common
power supply circuitry. There’s no doubt
that a Model 47A 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 audio cables. But it’s likely
that a significant “ground loop” would be
created through pin 1 of each of the Model
47A’s 2-wire interfaces. While it’s possible
to use a set of special isolation transformers
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
2-channel intercom circuit. Check it out!