Creating a simple System Power macro.
Let�s go through a simple 3-device power macro using components that lack any discrete power codes. First, create three new variables to track the power state of each device: �TV Power�, �Receiver Power� and �DVR Power�. You�ll then need a screen with two buttons for each of these devices: one for �Device On� and another for �Device Off�. For each of those six buttons, change the macro type to �Variable�, and select the correct variable to monitor.
 A simple variable-based "Power Off" macro.
For the Power On macro for each device, select the �Variable=0� macro tab and add two commands: the first one with the device�s actual toggle power code, and a second command setting the device�s variable to �1�. Leave the �Variable=1� tab blank. For the Power Off macro do the opposite: select the �Variable=1� macro tab and again add two commands, one with the toggle power code but the second should instead set the device�s variable to �0�. Leave the �Variable=0� tab blank.
To assemble these together, link your master �System On� button to the three �Power On� macros, and the �System Off� button to the three �Power Off� macros.
Now, each time any of those �Power On� macros are run, the remote will first check the status of the variable. If �0� or �off�, it performs all steps on the �Variable=0� tab: sending the device�s power command and then changing the variable to �1�. If that same macro is run a second time, perhaps by accident, well the variable now reads �1�, so it only performs commands on the �Variable=1� tab, which has been left blank and thus has no effect on the system: the device remains powered on! If your remote configuration has user-accessible �Power� buttons for any variable-controlled device, it would be a good idea to also add an �Invert State� variable command to those buttons so that the remote knows if the user has later turned a device on or off. Finally, when the user is finished and runs the �System Off� macro, only those devices that have their variable set to �1� will have the power command transmitted.
The downside of internal variables.
Variables are a great way to offer some form of automation on troublesome TOADs (Toggle-Only Actuated Devices) without the expense of URC�s optional MSC-400 backend system, but internal variables by their very nature aren�t bulletproof. It�s always going to be possible for the remote to become out of sync with the device, meaning that it thinks the device is on when it�s really off, either due to a power outage, missed command, someone walking up to a device and turning it on/off, and so forth.
This is why devices such as the MSC-400 offer device status sensors, so it�s possible to know the true state of a component rather than simply making educated guesses. This is also why the Logitech Harmony (which also makes use of internal variables) has a prominent �Help� button whose main purpose is to help users re-synchronize the remote with the actual status of their A/V components. MX-900, KP-900 and TX-1000 programmers who want to make use of internal variables would be recommended to implement their own [Help] button, thus allowing users to easily correct potential out-of-sync situations.
Regardless, this is a very practical addition to an already quite capable remote.
- Daniel Tonks (Remote Central)
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