Hi Lucas, at this rate you'll be showing the tech what to do!

Yes, your ducted unit is one for a multi so it will be one of the LMAW4's. The outdoor unit has the main power supply, then the this will be fed down the interconnect to each indoor unit. To find out which one is your outdoor unit, turn the breaker off then check which outdoor unit has no power. If more than one has no power then turn the breaker back on and find which one now has power.
The outdoor unit has to have power so your indoor unit can power the remote and get the fault code up.

Next up you said the error was comms and the breaker tripped so it isn't looking like a cheap repair unfortunately. Chances are something has let go outside and now the outdoor PCB's aren't powering up so they can't communicate with the indoors.
Outside has 3 PCB's. Power supply board is first up, easy to check, power goes in and comes out.
This power then goes into the main (big) PCB. At first power up the current here will first go through a thermal fuse (posistor), if all is fine everything should power up and a relay will close to short across the posistor so full current can go though. If too much current the posistor will go open circuit and voltage will go no further as a protection device. From there it will go through a rectifier (so now DC voltage) and into the third board - Active Filter Module (ACTPM for short). It then goes back into the main PCB and this DC (and actively filtered!) voltage gets stepped down to power the IC's.

Chances are the compressor or fan motor has packed up and taken out main and/or ACTPM. The fan motors in these units had some troubles back in the day. Sometimes on power up the fan motor (which has it's own PCB in the back of the motor) would spike back to the main PCB taking both items out. Old motors had a metal body, new type were a white plastic.
If you are a bit handy with the tools and you can confirm which unit is yours then first off megger the compressor and check for any blown PCB's. If you're not sure on that let me know, it's straight forward really.

Cheers,
Andy.