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!
