Gary Liebisch posted:... So I had concluded that there was no isolation between the power used to operate the IR circuit and the power sent to the switched accessory.
Perhaps semantics, but there is "some" isolation. I didn't draw out a full schematic but I did open up a 153IR to see what makes it tick. See this post.
This new diagram might be of use to your question about DC operation and isolation.
What's implied but not spelled out in the 153IR manual/documentation are the internal connection of the common input and the "C" of the internal 153IR relay. This is drawn as the black line inside the box.
The two power wires go to a bridge rectifier which converts AC or DC to the low-voltage DC to operate the internal electronics (IR sensors, timing) and ultimately drive the internal DC coil relay.
Let's say you have 4 accessories that all operate at different voltages. Some may be AC, some may be DC. As long as the DC power source is isolated (such as a wall-wart), you can tie its common to the AC accessory common. The 153IR can then switch common to all 4 accessories each operating at a difference voltage (subject to the 3 Amp total capacity of the 153IR internal relay). As drawn, accessory #4 is operating on 12V DC so this accessory could be a 12V DC relay to then switch even more power if 3A is not enough.
